81643264 has 18 divisors (see below), whose sum is σ = 162968120. Its totient is φ = 40821504.

The previous prime is 81643253. The next prime is 81643279. The reversal of 81643264 is 46234618.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159204 + ... + 159715.

Almost surely, 2^81643264 is an apocalyptic number.

It is an amenable number.

81643264 is a deficient number, since it is larger than the sum of its proper divisors (81324856).

81643264 is an equidigital number, since it uses as much as digits as its factorization.

81643264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 318935 (or 318921 counting only the distinct ones).

The product of its digits is 27648, while the sum is 34.

The square root of 81643264 is about 9035.6662178281. Note that the first 3 decimals coincide. The cubic root of 81643264 is about 433.8172193575.

The spelling of 81643264 in words is "eighty-one million, six hundred forty-three thousand, two hundred sixty-four".