21261231261513 has 24 divisors (see below), whose sum is σ = 31599917111880. Its totient is φ = 13769027001600.

The previous prime is 21261231261511. The next prime is 21261231261539. The reversal of 21261231261513 is 31516213216212.

21261231261513 is a `hidden beast` number, since 2 + 1 + 2 + 6 + 1 + 2 + 31 + 2 + 615 + 1 + 3 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 8624400713289 + 12636830548224 = 2936733^2 + 3554832^2 .

It is not a de Polignac number, because 21261231261513 - 2¹ = 21261231261511 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21261231261511) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 220609308 + ... + 220705661.

It is an arithmetic number, because the mean of its divisors is an integer number (1316663212995).

Almost surely, 2^{21261231261513} is an apocalyptic number.

It is an amenable number.

21261231261513 is a deficient number, since it is larger than the sum of its proper divisors (10338685850367).

21261231261513 is a wasteful number, since it uses less digits than its factorization.

21261231261513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 441315129 (or 441315126 counting only the distinct ones).

The product of its digits is 25920, while the sum is 36.

Adding to 21261231261513 its reverse (31516213216212), we get a palindrome (52777444477725).

The spelling of 21261231261513 in words is "twenty-one trillion, two hundred sixty-one billion, two hundred thirty-one million, two hundred sixty-one thousand, five hundred thirteen".