131220021 has 4 divisors (see below), whose sum is σ = 174960032. Its totient is φ = 87480012.

The previous prime is 131220017. The next prime is 131220029. The reversal of 131220021 is 120022131.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 131220021 - 2² = 131220017 is a prime.

It is a super-2 number, since 2×131220021² = 34437387822480882, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 131219979 and 131220006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (131220029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21870001 + ... + 21870006.

It is an arithmetic number, because the mean of its divisors is an integer number (43740008).

Almost surely, 2^131220021 is an apocalyptic number.

It is an amenable number.

131220021 is a deficient number, since it is larger than the sum of its proper divisors (43740011).

131220021 is an equidigital number, since it uses as much as digits as its factorization.

131220021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43740010.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 131220021 is about 11455.1307718419. The cubic root of 131220021 is about 508.1594827038.

Adding to 131220021 its reverse (120022131), we get a palindrome (251242152).

The spelling of 131220021 in words is "one hundred thirty-one million, two hundred twenty thousand, twenty-one".