15561660420 has 144 divisors (see below), whose sum is σ = 48899214000. Its totient is φ = 4001120256.

The previous prime is 15561660409. The next prime is 15561660461. The reversal of 15561660420 is 2406616551.

15561660420 is a `hidden beast` number, since 1 + 556 + 1 + 6 + 60 + 42 + 0 = 666.

It can be written as a sum of positive squares in 8 ways, for example, as 1829101824 + 13732558596 = 42768^2 + 117186^2 .

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 47 ways as a sum of consecutive naturals, for example, 4847776 + ... + 4850984.

It is an arithmetic number, because the mean of its divisors is an integer number (339577875).

Almost surely, 2^15561660420 is an apocalyptic number.

15561660420 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 15561660420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24449607000).

15561660420 is an abundant number, since it is smaller than the sum of its proper divisors (33337553580).

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

15561660420 is a wasteful number, since it uses less digits than its factorization.

15561660420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4182 (or 4177 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

The spelling of 15561660420 in words is "fifteen billion, five hundred sixty-one million, six hundred sixty thousand, four hundred twenty".