81657215 has 16 divisors (see below), whose sum is σ = 100980000. Its totient is φ = 63353472.

The previous prime is 81657209. The next prime is 81657287. The reversal of 81657215 is 51275618.

It is a cyclic number.

It is not a de Polignac number, because 81657215 - 2⁸ = 81656959 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30761 + ... + 33309.

It is an arithmetic number, because the mean of its divisors is an integer number (6311250).

Almost surely, 2^81657215 is an apocalyptic number.

81657215 is a deficient number, since it is larger than the sum of its proper divisors (19322785).

81657215 is a wasteful number, since it uses less digits than its factorization.

81657215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2746.

The product of its digits is 16800, while the sum is 35.

The square root of 81657215 is about 9036.4381810534. The cubic root of 81657215 is about 433.8419278231.

The spelling of 81657215 in words is "eighty-one million, six hundred fifty-seven thousand, two hundred fifteen".