15216401661 has 4 divisors (see below), whose sum is σ = 20288535552. Its totient is φ = 10144267772.

The previous prime is 15216401657. The next prime is 15216401687. The reversal of 15216401661 is 16610461251.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 15216401661 - 2² = 15216401657 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15216401461) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2536066941 + ... + 2536066946.

It is an arithmetic number, because the mean of its divisors is an integer number (5072133888).

Almost surely, 2^15216401661 is an apocalyptic number.

It is an amenable number.

15216401661 is a deficient number, since it is larger than the sum of its proper divisors (5072133891).

15216401661 is an equidigital number, since it uses as much as digits as its factorization.

15216401661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5072133890.

The product of its (nonzero) digits is 8640, while the sum is 33.

The spelling of 15216401661 in words is "fifteen billion, two hundred sixteen million, four hundred one thousand, six hundred sixty-one".