81431657 has 4 divisors (see below), whose sum is σ = 81453456. Its totient is φ = 81409860.

The previous prime is 81431653. The next prime is 81431659. The reversal of 81431657 is 75613418.

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 a cyclic number.

It is not a de Polignac number, because 81431657 - 2² = 81431653 is a prime.

It is a super-2 number, since 2×81431657² = 13262229523531298, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81431653) 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, 3719 + ... + 13292.

It is an arithmetic number, because the mean of its divisors is an integer number (20363364).

Almost surely, 2^81431657 is an apocalyptic number.

It is an amenable number.

81431657 is a deficient number, since it is larger than the sum of its proper divisors (21799).

81431657 is a wasteful number, since it uses less digits than its factorization.

81431657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21798.

The product of its digits is 20160, while the sum is 35.

The square root of 81431657 is about 9023.9490800868. The cubic root of 81431657 is about 433.4420988648.

The spelling of 81431657 in words is "eighty-one million, four hundred thirty-one thousand, six hundred fifty-seven".