81660780 has 36 divisors (see below), whose sum is σ = 247704912. Its totient is φ = 21776160.

The previous prime is 81660773. The next prime is 81660797. The reversal of 81660780 is 8706618.

It is a tau number, because it is divible by the number of its divisors (36).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct 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 11 ways as a sum of consecutive naturals, for example, 226656 + ... + 227015.

It is an arithmetic number, because the mean of its divisors is an integer number (6880692).

Almost surely, 2^81660780 is an apocalyptic number.

It is an amenable number.

81660780 is an abundant number, since it is smaller than the sum of its proper divisors (166044132).

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

81660780 is a wasteful number, since it uses less digits than its factorization.

81660780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 453686 (or 453681 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The square root of 81660780 is about 9036.6354358246. The cubic root of 81660780 is about 433.8482413046.

The spelling of 81660780 in words is "eighty-one million, six hundred sixty thousand, seven hundred eighty".