131211821 has 4 divisors (see below), whose sum is σ = 141305052. Its totient is φ = 121118592.

The previous prime is 131211781. The next prime is 131211851. The reversal of 131211821 is 128112131.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 128112131 = 7 ⋅18301733.

It can be written as a sum of positive squares in 2 ways, for example, as 87796900 + 43414921 = 9370^2 + 6589^2 .

It is a cyclic number.

It is not a de Polignac number, because 131211821 - 2¹⁸ = 130949677 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 131211793 and 131211802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (131211851) 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, 5046596 + ... + 5046621.

It is an arithmetic number, because the mean of its divisors is an integer number (35326263).

Almost surely, 2^131211821 is an apocalyptic number.

It is an amenable number.

131211821 is a deficient number, since it is larger than the sum of its proper divisors (10093231).

131211821 is a wasteful number, since it uses less digits than its factorization.

131211821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10093230.

The product of its digits is 96, while the sum is 20.

The square root of 131211821 is about 11454.7728480315. The cubic root of 131211821 is about 508.1488974427.

Adding to 131211821 its reverse (128112131), we get a palindrome (259323952).

The spelling of 131211821 in words is "one hundred thirty-one million, two hundred eleven thousand, eight hundred twenty-one".