81901666 has 64 divisors (see below), whose sum is σ = 168376320. Its totient is φ = 28892160.

The previous prime is 81901649. The next prime is 81901667. The reversal of 81901666 is 66610918.

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (81901667) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 66690 + ... + 67906.

It is an arithmetic number, because the mean of its divisors is an integer number (2630880).

Almost surely, 2^81901666 is an apocalyptic number.

81901666 is an abundant number, since it is smaller than the sum of its proper divisors (86474654).

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

81901666 is a wasteful number, since it uses less digits than its factorization.

81901666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1279.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 81901666 is about 9049.9539225346. The cubic root of 81901666 is about 434.2744164119.

The spelling of 81901666 in words is "eighty-one million, nine hundred one thousand, six hundred sixty-six".