81637408 has 12 divisors (see below), whose sum is σ = 160723710. Its totient is φ = 40818688.

The previous prime is 81637397. The next prime is 81637421. The reversal of 81637408 is 80473618.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 80496784 + 1140624 = 8972^2 + 1068^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1275553 + ... + 1275616.

Almost surely, 2^81637408 is an apocalyptic number.

It is an amenable number.

81637408 is a deficient number, since it is larger than the sum of its proper divisors (79086302).

81637408 is a wasteful number, since it uses less digits than its factorization.

81637408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2551179 (or 2551171 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 37.

The square root of 81637408 is about 9035.3421628625. The cubic root of 81637408 is about 433.8068470203.

The spelling of 81637408 in words is "eighty-one million, six hundred thirty-seven thousand, four hundred eight".