661210813920 has 192 divisors, whose sum is σ = 2206063641600. Its totient is φ = 165895938048.

The previous prime is 661210813891. The next prime is 661210813951. The reversal of 661210813920 is 29318012166.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28246381 + ... + 28269779.

It is an arithmetic number, because the mean of its divisors is an integer number (11489914800).

Almost surely, 2^661210813920 is an apocalyptic number.

661210813920 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 661210813920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1103031820800).

661210813920 is an abundant number, since it is smaller than the sum of its proper divisors (1544852827680).

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

661210813920 is a wasteful number, since it uses less digits than its factorization.

661210813920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26897 (or 26889 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 39.

The spelling of 661210813920 in words is "six hundred sixty-one billion, two hundred ten million, eight hundred thirteen thousand, nine hundred twenty".