81638402 has 8 divisors (see below), whose sum is σ = 128902800. Its totient is φ = 38670804.

The previous prime is 81638399. The next prime is 81638411. The reversal of 81638402 is 20483618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×81638402² = 13329657362227208, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1074152 + ... + 1074227.

It is an arithmetic number, because the mean of its divisors is an integer number (16112850).

Almost surely, 2^81638402 is an apocalyptic number.

81638402 is a deficient number, since it is larger than the sum of its proper divisors (47264398).

81638402 is a wasteful number, since it uses less digits than its factorization.

81638402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2148400.

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 81638402 is about 9035.3971689129. The cubic root of 81638402 is about 433.8086076603.

The spelling of 81638402 in words is "eighty-one million, six hundred thirty-eight thousand, four hundred two".