81666624 has 56 divisors (see below), whose sum is σ = 232704640. Its totient is φ = 25127424.

The previous prime is 81666619. The next prime is 81666631. The reversal of 81666624 is 42666618.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a nude number because it is divisible by every one of its digits.

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, 13864 + ... + 18855.

It is an arithmetic number, because the mean of its divisors is an integer number (4155440).

Almost surely, 2^81666624 is an apocalyptic number.

It is an amenable number.

81666624 is an abundant number, since it is smaller than the sum of its proper divisors (151038016).

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

81666624 is a wasteful number, since it uses less digits than its factorization.

81666624 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32747 (or 32737 counting only the distinct ones).

The product of its digits is 82944, while the sum is 39.

The square root of 81666624 is about 9036.9587804748. The cubic root of 81666624 is about 433.8585904124.

The spelling of 81666624 in words is "eighty-one million, six hundred sixty-six thousand, six hundred twenty-four".