81505764 has 30 divisors (see below), whose sum is σ = 213073014. Its totient is φ = 27168480.

The previous prime is 81505759. The next prime is 81505777. The reversal of 81505764 is 46750518.

81505764 is a `hidden beast` number, since 81 + 5 + 0 + 576 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 43164900 + 38340864 = 6570^2 + 6192^2 .

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 125457 + ... + 126104.

Almost surely, 2^81505764 is an apocalyptic number.

It is an amenable number.

81505764 is an abundant number, since it is smaller than the sum of its proper divisors (131567250).

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

81505764 is a wasteful number, since it uses less digits than its factorization.

81505764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 251577 (or 251566 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

The square root of 81505764 is about 9028.0542754239. The cubic root of 81505764 is about 433.5735438736.

The spelling of 81505764 in words is "eighty-one million, five hundred five thousand, seven hundred sixty-four".