15640772721 has 32 divisors (see below), whose sum is σ = 24015052800. Its totient is φ = 8869635264.

The previous prime is 15640772699. The next prime is 15640772759. The reversal of 15640772721 is 12727704651.

It is not a de Polignac number, because 15640772721 - 2¹⁰ = 15640771697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (15640771721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 6453916 + ... + 6456338.

It is an arithmetic number, because the mean of its divisors is an integer number (750470400).

Almost surely, 2^15640772721 is an apocalyptic number.

It is an amenable number.

15640772721 is a deficient number, since it is larger than the sum of its proper divisors (8374280079).

15640772721 is a wasteful number, since it uses less digits than its factorization.

15640772721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4645.

The product of its (nonzero) digits is 164640, while the sum is 42.

The spelling of 15640772721 in words is "fifteen billion, six hundred forty million, seven hundred seventy-two thousand, seven hundred twenty-one".