16368387721 has 21 divisors (see below), whose sum is σ = 19147763271. Its totient is φ = 13992432552.

The previous prime is 16368387701. The next prime is 16368387733. The reversal of 16368387721 is 12778386361.

The square root of 16368387721 is 127939.

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., 8897205625 + 7471182096 = 94325^2 + 86436^2 .

It is not a de Polignac number, because 16368387721 - 2⁵ = 16368387689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16368387701) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 43882891 + ... + 43883263.

It is an arithmetic number, because the mean of its divisors is an integer number (911798251).

Almost surely, 2^16368387721 is an apocalyptic number.

16368387721 is the 127939-th square number.

16368387721 is the 63970-th centered octagonal number.

It is an amenable number.

16368387721 is a deficient number, since it is larger than the sum of its proper divisors (2779375550).

16368387721 is an frugal number, since it uses more digits than its factorization.

16368387721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 788 (or 380 counting only the distinct ones).

The product of its digits is 2032128, while the sum is 52.

The spelling of 16368387721 in words is "sixteen billion, three hundred sixty-eight million, three hundred eighty-seven thousand, seven hundred twenty-one".