81057213 has 16 divisors (see below), whose sum is σ = 120225600. Its totient is φ = 53974800.

The previous prime is 81057199. The next prime is 81057257. The reversal of 81057213 is 31275018.

81057213 is a `hidden beast` number, since 81 + 0 + 572 + 13 = 666.

It is not a de Polignac number, because 81057213 - 2⁵ = 81057181 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81057293) 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, 38143 + ... + 40211.

It is an arithmetic number, because the mean of its divisors is an integer number (7514100).

Almost surely, 2^81057213 is an apocalyptic number.

It is an amenable number.

81057213 is a deficient number, since it is larger than the sum of its proper divisors (39168387).

81057213 is a wasteful number, since it uses less digits than its factorization.

81057213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3529 (or 3523 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 81057213 is about 9003.1779389280. The cubic root of 81057213 is about 432.7767180113.

The spelling of 81057213 in words is "eighty-one million, fifty-seven thousand, two hundred thirteen".