21129238881 has 45 divisors (see below), whose sum is σ = 32677170339. Its totient is φ = 13605602400.

The previous prime is 21129238873. The next prime is 21129238883. The reversal of 21129238881 is 18883292112.

The square root of 21129238881 is 145359.

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., 6059221281 + 15070017600 = 77841^2 + 122760^2 .

It is not a de Polignac number, because 21129238881 - 2³ = 21129238873 is a prime.

It is a super-2 number, since 2×21129238881² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21129238883) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 40554901 + ... + 40555421.

Almost surely, 2^21129238881 is an apocalyptic number.

21129238881 is the 145359-th square number.

21129238881 is the 72680-th centered octagonal number.

It is an amenable number.

21129238881 is a deficient number, since it is larger than the sum of its proper divisors (11547931458).

21129238881 is an frugal number, since it uses more digits than its factorization.

21129238881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1116 (or 555 counting only the distinct ones).

The product of its digits is 110592, while the sum is 45.

The spelling of 21129238881 in words is "twenty-one billion, one hundred twenty-nine million, two hundred thirty-eight thousand, eight hundred eighty-one".