81639567 has 12 divisors (see below), whose sum is σ = 119684760. Its totient is φ = 53613648.

The previous prime is 81639527. The next prime is 81639587. The reversal of 81639567 is 76593618.

It is a happy number.

81639567 is a `hidden beast` number, since 8 + 1 + 639 + 5 + 6 + 7 = 666.

It is not a de Polignac number, because 81639567 - 2¹² = 81635471 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81639527) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 67092 + ... + 68297.

It is an arithmetic number, because the mean of its divisors is an integer number (9973730).

Almost surely, 2^81639567 is an apocalyptic number.

81639567 is a deficient number, since it is larger than the sum of its proper divisors (38045193).

81639567 is a wasteful number, since it uses less digits than its factorization.

81639567 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135462 (or 135459 counting only the distinct ones).

The product of its digits is 272160, while the sum is 45.

The square root of 81639567 is about 9035.4616373487. The cubic root of 81639567 is about 433.8106711689.

The spelling of 81639567 in words is "eighty-one million, six hundred thirty-nine thousand, five hundred sixty-seven".