661897958400 has 792 divisors, whose sum is σ = 2827664226240. Its totient is φ = 151283220480.

The previous prime is 661897958377. The next prime is 661897958429. The reversal of 661897958400 is 4859798166.

661897958400 is a `hidden beast` number, since 6 + 61 + 89 + 7 + 95 + 8 + 400 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 33859029 + ... + 33878571.

Almost surely, 2^661897958400 is an apocalyptic number.

661897958400 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 661897958400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1413832113120).

661897958400 is an abundant number, since it is smaller than the sum of its proper divisors (2165766267840).

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

661897958400 is a wasteful number, since it uses less digits than its factorization.

661897958400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19596 (or 19560 counting only the distinct ones).

The product of its (nonzero) digits is 26127360, while the sum is 63.

The spelling of 661897958400 in words is "six hundred sixty-one billion, eight hundred ninety-seven million, nine hundred fifty-eight thousand, four hundred".