661639644 has 24 divisors (see below), whose sum is σ = 1715362320. Its totient is φ = 220546512.

The previous prime is 661639639. The next prime is 661639687. The reversal of 661639644 is 446936166.

661639644 is a `hidden beast` number, since 6 + 6 + 1 + 639 + 6 + 4 + 4 = 666.

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

It is a self number, because there is not a number n which added to its sum of digits gives 661639644.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3063039 + ... + 3063254.

It is an arithmetic number, because the mean of its divisors is an integer number (71473430).

Almost surely, 2^661639644 is an apocalyptic number.

It is an amenable number.

661639644 is an abundant number, since it is smaller than the sum of its proper divisors (1053722676).

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

661639644 is a wasteful number, since it uses less digits than its factorization.

661639644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6126306 (or 6126298 counting only the distinct ones).

The product of its digits is 559872, while the sum is 45.

The square root of 661639644 is about 25722.3568904562. The cubic root of 661639644 is about 871.3791680468.

The spelling of 661639644 in words is "six hundred sixty-one million, six hundred thirty-nine thousand, six hundred forty-four".