81757881 has 24 divisors (see below), whose sum is σ = 122653440. Its totient is φ = 52423200.

The previous prime is 81757877. The next prime is 81757919. The reversal of 81757881 is 18875718.

It is not a de Polignac number, because 81757881 - 2² = 81757877 is a prime.

It is a super-2 number, since 2×81757881² = 13368702211220322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81757831) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49690 + ... + 51308.

It is an arithmetic number, because the mean of its divisors is an integer number (5110560).

Almost surely, 2^81757881 is an apocalyptic number.

It is an amenable number.

81757881 is a deficient number, since it is larger than the sum of its proper divisors (40895559).

81757881 is a wasteful number, since it uses less digits than its factorization.

81757881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1837 (or 1834 counting only the distinct ones).

The product of its digits is 125440, while the sum is 45.

The square root of 81757881 is about 9042.0064698053. The cubic root of 81757881 is about 434.0201329260.

The spelling of 81757881 in words is "eighty-one million, seven hundred fifty-seven thousand, eight hundred eighty-one".