15661431720 has 576 divisors, whose sum is σ = 59754240000. Its totient is φ = 3544611840.

The previous prime is 15661431703. The next prime is 15661431761. The reversal of 15661431720 is 2713416651.

15661431720 is a `hidden beast` number, since 1 + 5 + 6 + 614 + 3 + 17 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 105110206 + ... + 105110354.

It is an arithmetic number, because the mean of its divisors is an integer number (103740000).

Almost surely, 2^15661431720 is an apocalyptic number.

15661431720 is a gapful number since it is divisible by the number (10) 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 15661431720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29877120000).

15661431720 is an abundant number, since it is smaller than the sum of its proper divisors (44092808280).

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

15661431720 is a wasteful number, since it uses less digits than its factorization.

15661431720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 334 (or 316 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 36.

The spelling of 15661431720 in words is "fifteen billion, six hundred sixty-one million, four hundred thirty-one thousand, seven hundred twenty".