81616660 has 24 divisors (see below), whose sum is σ = 181477800. Its totient is φ = 30726144.

The previous prime is 81616657. The next prime is 81616679. The reversal of 81616660 is 6661618.

It can be written as a sum of positive squares in 4 ways, for example, as 23155344 + 58461316 = 4812^2 + 7646^2 .

It is a super-2 number, since 2×81616660² = 13322558379111200, which contains 22 as substring.

It is a hoax number, since the sum of its digits (34) 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 (34).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 119685 + ... + 120364.

It is an arithmetic number, because the mean of its divisors is an integer number (7561575).

Almost surely, 2^81616660 is an apocalyptic number.

It is an amenable number.

81616660 is an abundant number, since it is smaller than the sum of its proper divisors (99861140).

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

81616660 is a wasteful number, since it uses less digits than its factorization.

81616660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 240075 (or 240073 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 34.

The square root of 81616660 is about 9034.1939319455. The cubic root of 81616660 is about 433.7700934973.

The spelling of 81616660 in words is "eighty-one million, six hundred sixteen thousand, six hundred sixty".