661851640 has 16 divisors (see below), whose sum is σ = 1489166280. Its totient is φ = 264740640.

The previous prime is 661851587. The next prime is 661851649. The reversal of 661851640 is 46158166.

It is a self number, because there is not a number n which added to its sum of digits gives 661851640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661851649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8273106 + ... + 8273185.

Almost surely, 2^661851640 is an apocalyptic number.

It is an amenable number.

661851640 is an abundant number, since it is smaller than the sum of its proper divisors (827314640).

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

661851640 is a wasteful number, since it uses less digits than its factorization.

661851640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16546302 (or 16546298 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 37.

The square root of 661851640 is about 25726.4774114141. The cubic root of 661851640 is about 871.4722243268.

The spelling of 661851640 in words is "six hundred sixty-one million, eight hundred fifty-one thousand, six hundred forty".