81357732 has 18 divisors (see below), whose sum is σ = 205654358. Its totient is φ = 27119232.

The previous prime is 81357623. The next prime is 81357781. The reversal of 81357732 is 23775318.

81357732 is a `hidden beast` number, since 81 + 3 + 577 + 3 + 2 = 666.

It can be written as a sum of positive squares in only one way, i.e., 66194496 + 15163236 = 8136^2 + 3894^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 2259937 = 81357732 / (8 + 1 + 3 + 5 + 7 + 7 + 3 + 2).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1129933 + ... + 1130004.

Almost surely, 2^81357732 is an apocalyptic number.

It is an amenable number.

81357732 is an abundant number, since it is smaller than the sum of its proper divisors (124296626).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81357732 is a wasteful number, since it uses less digits than its factorization.

81357732 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2259947 (or 2259942 counting only the distinct ones).

The product of its digits is 35280, while the sum is 36.

The square root of 81357732 is about 9019.8521052177. The cubic root of 81357732 is about 433.3108971947.

The spelling of 81357732 in words is "eighty-one million, three hundred fifty-seven thousand, seven hundred thirty-two".