131221820 has 12 divisors (see below), whose sum is σ = 275565864. Its totient is φ = 52488720.

The previous prime is 131221817. The next prime is 131221823. The reversal of 131221820 is 28122131.

It is an interprime number because it is at equal distance from previous prime (131221817) and next prime (131221823).

It is a super-2 number, since 2×131221820² = 34438332088224800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 6561091 = 131221820 / (1 + 3 + 1 + 2 + 2 + 1 + 8 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 131221792 and 131221801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (131221823) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3280526 + ... + 3280565.

It is an arithmetic number, because the mean of its divisors is an integer number (22963822).

Almost surely, 2^131221820 is an apocalyptic number.

131221820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

131221820 is an abundant number, since it is smaller than the sum of its proper divisors (144344044).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

131221820 is a wasteful number, since it uses less digits than its factorization.

131221820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6561100 (or 6561098 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 131221820 is about 11455.2092953381. The cubic root of 131221820 is about 508.1618049478.

Adding to 131221820 its reverse (28122131), we get a palindrome (159343951).

It can be divided in two parts, 1312 and 21820, that added together give a palindrome (23132).

The spelling of 131221820 in words is "one hundred thirty-one million, two hundred twenty-one thousand, eight hundred twenty".