81668013 has 16 divisors (see below), whose sum is σ = 124575360. Its totient is φ = 46619136.

The previous prime is 81667951. The next prime is 81668033. The reversal of 81668013 is 31086618.

It is a de Polignac number, because none of the positive numbers 2^k-81668013 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81668033) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32581 + ... + 34997.

It is an arithmetic number, because the mean of its divisors is an integer number (7785960).

Almost surely, 2^81668013 is an apocalyptic number.

It is an amenable number.

81668013 is a deficient number, since it is larger than the sum of its proper divisors (42907347).

81668013 is a wasteful number, since it uses less digits than its factorization.

81668013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4036.

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 81668013 is about 9037.0356312233. The cubic root of 81668013 is about 433.8610501123.

The spelling of 81668013 in words is "eighty-one million, six hundred sixty-eight thousand, thirteen".