661564661120 has 256 divisors, whose sum is σ = 1795085107200. Its totient is φ = 230965862400.

The previous prime is 661564661113. The next prime is 661564661123. The reversal of 661564661120 is 21166465166.

It is a super-4 number, since 4×661564661120⁴ (a number of 48 digits) contains 4444 as substring.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661564661123) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 27704546 + ... + 27728414.

It is an arithmetic number, because the mean of its divisors is an integer number (7012051200).

Almost surely, 2^661564661120 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 661564661120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (897542553600).

661564661120 is an abundant number, since it is smaller than the sum of its proper divisors (1133520446080).

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

661564661120 is a wasteful number, since it uses less digits than its factorization.

661564661120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24057 (or 24045 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 44.

It can be divided in two parts, 6615646 and 61120, that added together give a palindrome (6676766).

The spelling of 661564661120 in words is "six hundred sixty-one billion, five hundred sixty-four million, six hundred sixty-one thousand, one hundred twenty".