81501666 has 32 divisors (see below), whose sum is σ = 171859968. Its totient is φ = 25728720.

The previous prime is 81501643. The next prime is 81501671. The reversal of 81501666 is 66610518.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4081 + ... + 13403.

It is an arithmetic number, because the mean of its divisors is an integer number (5370624).

Almost surely, 2^81501666 is an apocalyptic number.

81501666 is an abundant number, since it is smaller than the sum of its proper divisors (90358302).

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

81501666 is a wasteful number, since it uses less digits than its factorization.

81501666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9406.

The product of its (nonzero) digits is 8640, while the sum is 33.

The square root of 81501666 is about 9027.8273133684. The cubic root of 81501666 is about 433.5662772539.

The spelling of 81501666 in words is "eighty-one million, five hundred one thousand, six hundred sixty-six".