661363920 has 640 divisors, whose sum is σ = 2879815680. Its totient is φ = 136028160.

The previous prime is 661363909. The next prime is 661363933. The reversal of 661363920 is 29363166.

661363920 is a `hidden beast` number, since 6 + 6 + 13 + 639 + 2 + 0 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 7968199 + ... + 7968281.

It is an arithmetic number, because the mean of its divisors is an integer number (4499712).

Almost surely, 2^661363920 is an apocalyptic number.

661363920 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 661363920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1439907840).

661363920 is an abundant number, since it is smaller than the sum of its proper divisors (2218451760).

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

661363920 is a wasteful number, since it uses less digits than its factorization.

661363920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 160 (or 148 counting only the distinct ones).

The product of its (nonzero) digits is 34992, while the sum is 36.

The square root of 661363920 is about 25716.9967142355. The cubic root of 661363920 is about 871.2581084267.

The spelling of 661363920 in words is "six hundred sixty-one million, three hundred sixty-three thousand, nine hundred twenty".