231621581 has 2 divisors, whose sum is σ = 231621582. Its totient is φ = 231621580.

The previous prime is 231621563. The next prime is 231621623. The reversal of 231621581 is 185126132.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 230736100 + 885481 = 15190^2 + 941^2 .

It is a cyclic number.

It is not a de Polignac number, because 231621581 - 2¹⁴ = 231605197 is a prime.

It is a super-2 number, since 2×231621581² = 107297113569879122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231621541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115810790 + 115810791.

It is an arithmetic number, because the mean of its divisors is an integer number (115810791).

Almost surely, 2^231621581 is an apocalyptic number.

It is an amenable number.

231621581 is a deficient number, since it is larger than the sum of its proper divisors (1).

231621581 is an equidigital number, since it uses as much as digits as its factorization.

231621581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 29.

The square root of 231621581 is about 15219.1189298198. The cubic root of 231621581 is about 614.1290962410.

The spelling of 231621581 in words is "two hundred thirty-one million, six hundred twenty-one thousand, five hundred eighty-one".