661562335872 has 512 divisors, whose sum is σ = 2066002329600. Its totient is φ = 208113684480.

The previous prime is 661562335867. The next prime is 661562335879. The reversal of 661562335872 is 278533265166.

661562335872 is a `hidden beast` number, since 6 + 6 + 1 + 5 + 623 + 3 + 5 + 8 + 7 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (661562335879) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1493368483 + ... + 1493368925.

It is an arithmetic number, because the mean of its divisors is an integer number (4035160800).

Almost surely, 2^661562335872 is an apocalyptic number.

661562335872 is a gapful number since it is divisible by the number (62) 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 661562335872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1033001164800).

661562335872 is an abundant number, since it is smaller than the sum of its proper divisors (1404439993728).

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

661562335872 is a wasteful number, since it uses less digits than its factorization.

661562335872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 813 (or 795 counting only the distinct ones).

The product of its digits is 10886400, while the sum is 54.

The spelling of 661562335872 in words is "six hundred sixty-one billion, five hundred sixty-two million, three hundred thirty-five thousand, eight hundred seventy-two".