29261865721 has 9 divisors (see below), whose sum is σ = 32165937349. Its totient is φ = 26599985500.

The previous prime is 29261865719. The next prime is 29261865733. The reversal of 29261865721 is 12756816292.

The square root of 29261865721 is 171061.

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

It is not a de Polignac number, because 29261865721 - 2¹ = 29261865719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (29261865121) 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, 1873896 + ... + 1889446.

Almost surely, 2^29261865721 is an apocalyptic number.

29261865721 is the 171061-st square number.

29261865721 is the 85531-st centered octagonal number.

It is an amenable number.

29261865721 is a deficient number, since it is larger than the sum of its proper divisors (2904071628).

29261865721 is an frugal number, since it uses more digits than its factorization.

29261865721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31124 (or 15562 counting only the distinct ones).

The product of its digits is 725760, while the sum is 49.

Multiplying 29261865721 by its sum of digits (49), we get a square (1433831420329 = 1197427²).

The spelling of 29261865721 in words is "twenty-nine billion, two hundred sixty-one million, eight hundred sixty-five thousand, seven hundred twenty-one".