66511638 has 16 divisors (see below), whose sum is σ = 147803760. Its totient is φ = 22170528.

The previous prime is 66511597. The next prime is 66511649. The reversal of 66511638 is 83611566.

It is a happy number.

66511638 is a `hidden beast` number, since 6 + 6 + 5 + 11 + 638 = 666.

It is a Curzon number.

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, 615795 + ... + 615902.

It is an arithmetic number, because the mean of its divisors is an integer number (9237735).

Almost surely, 2^66511638 is an apocalyptic number.

66511638 is an abundant number, since it is smaller than the sum of its proper divisors (81292122).

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

66511638 is a wasteful number, since it uses less digits than its factorization.

66511638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1231708 (or 1231702 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

The square root of 66511638 is about 8155.4667554960. The cubic root of 66511638 is about 405.1655838695.

The spelling of 66511638 in words is "sixty-six million, five hundred eleven thousand, six hundred thirty-eight".