131231021 has 4 divisors (see below), whose sum is σ = 133707132. Its totient is φ = 128754912.

The previous prime is 131230999. The next prime is 131231027. The reversal of 131231021 is 120132131.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 120132131 = 7 ⋅17161733.

It can be written as a sum of positive squares in 2 ways, for example, as 83814025 + 47416996 = 9155^2 + 6886^2 .

It is a cyclic number.

It is not a de Polignac number, because 131231021 - 2¹⁰ = 131229997 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 131230987 and 131231005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (131231027) 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, 1237976 + ... + 1238081.

It is an arithmetic number, because the mean of its divisors is an integer number (33426783).

Almost surely, 2^131231021 is an apocalyptic number.

It is an amenable number.

131231021 is a deficient number, since it is larger than the sum of its proper divisors (2476111).

131231021 is an equidigital number, since it uses as much as digits as its factorization.

131231021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2476110.

The product of its (nonzero) digits is 36, while the sum is 14.

The square root of 131231021 is about 11455.6108959758. The cubic root of 131231021 is about 508.1736817518.

Adding to 131231021 its reverse (120132131), we get a palindrome (251363152).

The spelling of 131231021 in words is "one hundred thirty-one million, two hundred thirty-one thousand, twenty-one".