64661820 has 24 divisors (see below), whose sum is σ = 181053264. Its totient is φ = 17243136.

The previous prime is 64661813. The next prime is 64661873. The reversal of 64661820 is 2816646.

It is a happy 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, 538789 + ... + 538908.

It is an arithmetic number, because the mean of its divisors is an integer number (7543886).

Almost surely, 2^64661820 is an apocalyptic number.

64661820 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

64661820 is an abundant number, since it is smaller than the sum of its proper divisors (116391444).

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

64661820 is a wasteful number, since it uses less digits than its factorization.

64661820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1077709 (or 1077707 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 33.

The square root of 64661820 is about 8041.2573643678. The cubic root of 64661820 is about 401.3740661176.

The spelling of 64661820 in words is "sixty-four million, six hundred sixty-one thousand, eight hundred twenty".