81587691 has 24 divisors (see below), whose sum is σ = 128061440. Its totient is φ = 49863600.

The previous prime is 81587687. The next prime is 81587707. The reversal of 81587691 is 19678518.

81587691 is a `hidden beast` number, since 8 + 1 + 587 + 69 + 1 = 666.

It is not a de Polignac number, because 81587691 - 2² = 81587687 is a prime.

It is a super-2 number, since 2×81587691² = 13313102645422962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81587651) 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, 2395 + ... + 12996.

Almost surely, 2^81587691 is an apocalyptic number.

81587691 is a deficient number, since it is larger than the sum of its proper divisors (46473749).

81587691 is a wasteful number, since it uses less digits than its factorization.

81587691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15447 (or 15444 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 81587691 is about 9032.5904922121. The cubic root of 81587691 is about 433.7187666692.

The spelling of 81587691 in words is "eighty-one million, five hundred eighty-seven thousand, six hundred ninety-one".