664961220 has 144 divisors (see below), whose sum is σ = 2514814848. Its totient is φ = 138170880.

The previous prime is 664961207. The next prime is 664961233. The reversal of 664961220 is 22169466.

664961220 is a `hidden beast` number, since 6 + 649 + 6 + 1 + 2 + 2 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (664961207) and next prime (664961233).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 10129 + ... + 37848.

It is an arithmetic number, because the mean of its divisors is an integer number (17463992).

Almost surely, 2^664961220 is an apocalyptic number.

664961220 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 664961220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1257407424).

664961220 is an abundant number, since it is smaller than the sum of its proper divisors (1849853628).

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

664961220 is a wasteful number, since it uses less digits than its factorization.

664961220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48010 (or 48005 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

The square root of 664961220 is about 25786.8419935439. The cubic root of 664961220 is about 872.8349061734.

The spelling of 664961220 in words is "six hundred sixty-four million, nine hundred sixty-one thousand, two hundred twenty".