15661988761 has 6 divisors (see below), whose sum is σ = 15885692186. Its totient is φ = 15441392400.

The previous prime is 15661988747. The next prime is 15661988773. The reversal of 15661988761 is 16788916651.

It can be written as a sum of positive squares in only one way, i.e., 15526406025 + 135582736 = 124605^2 + 11644^2 .

It is not a de Polignac number, because 15661988761 - 2¹³ = 15661980569 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15661988696 and 15661988705.

It is not an unprimeable number, because it can be changed into a prime (15661998761) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1548420 + ... + 1558501.

Almost surely, 2^15661988761 is an apocalyptic number.

It is an amenable number.

15661988761 is a deficient number, since it is larger than the sum of its proper divisors (223703425).

15661988761 is an frugal number, since it uses more digits than its factorization.

15661988761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3107063 (or 3106992 counting only the distinct ones).

The product of its digits is 4354560, while the sum is 58.

The spelling of 15661988761 in words is "fifteen billion, six hundred sixty-one million, nine hundred eighty-eight thousand, seven hundred sixty-one".