21616938729 has 9 divisors (see below), whose sum is σ = 31225104183. Its totient is φ = 14410998432.

The previous prime is 21616938709. The next prime is 21616938731. The reversal of 21616938729 is 92783961612.

The square root of 21616938729 is 147027.

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., 43204329 + 21573734400 = 6573^2 + 146880^2 .

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 21616938729 - 2¹⁹ = 21616414441 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21616938709) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 416577 + ... + 465585.

Almost surely, 2^21616938729 is an apocalyptic number.

21616938729 is the 147027-th square number.

21616938729 is the 73514-th centered octagonal number.

It is an amenable number.

21616938729 is a deficient number, since it is larger than the sum of its proper divisors (9608165454).

21616938729 is an frugal number, since it uses more digits than its factorization.

21616938729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98024 (or 49012 counting only the distinct ones).

The product of its digits is 1959552, while the sum is 54.

The spelling of 21616938729 in words is "twenty-one billion, six hundred sixteen million, nine hundred thirty-eight thousand, seven hundred twenty-nine".