15661521316 has 45 divisors (see below), whose sum is σ = 31998761249. Its totient is φ = 6706824432.

The previous prime is 15661521313. The next prime is 15661521331. The reversal of 15661521316 is 61312516651.

The square root of 15661521316 is 125146.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 10288044900 + 5373476416 = 101430^2 + 73304^2 .

It is not an unprimeable number, because it can be changed into a prime (15661521313) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 12263670 + ... + 12264946.

Almost surely, 2^15661521316 is an apocalyptic number.

15661521316 is the 125146-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 15661521316

15661521316 is an abundant number, since it is smaller than the sum of its proper divisors (16337239933).

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

15661521316 is an frugal number, since it uses more digits than its factorization.

15661521316 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2586 (or 1286 counting only the distinct ones).

The product of its digits is 32400, while the sum is 37.

Multiplying 15661521316 by its product of digits (32400), we get a square (507433290638400 = 22526280²).

The spelling of 15661521316 in words is "fifteen billion, six hundred sixty-one million, five hundred twenty-one thousand, three hundred sixteen".