661404522688 has 224 divisors, whose sum is σ = 1702453491200. Its totient is φ = 247579877376.

The previous prime is 661404522619. The next prime is 661404522767. The reversal of 661404522688 is 886225404166.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (224).

It is a super-2 number, since 2×661404522688² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (52).

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, 103681483 + ... + 103687861.

It is an arithmetic number, because the mean of its divisors is an integer number (7600238800).

Almost surely, 2^661404522688 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661404522688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (851226745600).

661404522688 is an abundant number, since it is smaller than the sum of its proper divisors (1041048968512).

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

661404522688 is a wasteful number, since it uses less digits than its factorization.

661404522688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7367 (or 7357 counting only the distinct ones).

The product of its (nonzero) digits is 4423680, while the sum is 52.

The spelling of 661404522688 in words is "six hundred sixty-one billion, four hundred four million, five hundred twenty-two thousand, six hundred eighty-eight".