661913650944 has 864 divisors, whose sum is σ = 2523702272000. Its totient is φ = 165333934080.

The previous prime is 661913650913. The next prime is 661913650991. The reversal of 661913650944 is 449056319166.

It is a happy number.

661913650944 is a `hidden beast` number, since 6 + 6 + 1 + 91 + 3 + 6 + 509 + 44 = 666.

It is a super-2 number, since 2×661913650944² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 195195489 + ... + 195198879.

Almost surely, 2^661913650944 is an apocalyptic number.

661913650944 is a gapful number since it is divisible by the number (64) 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 661913650944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1261851136000).

661913650944 is an abundant number, since it is smaller than the sum of its proper divisors (1861788621056).

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

661913650944 is a wasteful number, since it uses less digits than its factorization.

661913650944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3466 (or 3435 counting only the distinct ones).

The product of its (nonzero) digits is 4199040, while the sum is 54.

The spelling of 661913650944 in words is "six hundred sixty-one billion, nine hundred thirteen million, six hundred fifty thousand, nine hundred forty-four".