661539510144 has 384 divisors, whose sum is σ = 2058643641600. Its totient is φ = 203152637952.

The previous prime is 661539510139. The next prime is 661539510197. The reversal of 661539510144 is 441015935166.

661539510144 is a `hidden beast` number, since 6 + 6 + 1 + 539 + 5 + 101 + 4 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (384).

It is a self number, because there is not a number n which added to its sum of digits gives 661539510144.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 219123867 + ... + 219126885.

It is an arithmetic number, because the mean of its divisors is an integer number (5361051150).

Almost surely, 2^661539510144 is an apocalyptic number.

661539510144 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 661539510144, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1029321820800).

661539510144 is an abundant number, since it is smaller than the sum of its proper divisors (1397104131456).

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

661539510144 is a wasteful number, since it uses less digits than its factorization.

661539510144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3290 (or 3275 counting only the distinct ones).

The product of its (nonzero) digits is 388800, while the sum is 45.

The spelling of 661539510144 in words is "six hundred sixty-one billion, five hundred thirty-nine million, five hundred ten thousand, one hundred forty-four".