21513256453 has 16 divisors (see below), whose sum is σ = 23578012080. Its totient is φ = 19510050816.

The previous prime is 21513256423. The next prime is 21513256459. The reversal of 21513256453 is 35465231512.

It can be written as a sum of positive squares in 8 ways, for example, as 448507684 + 21064748769 = 21178^2 + 145137^2 .

It is a cyclic number.

It is not a de Polignac number, because 21513256453 - 2⁹ = 21513255941 is a prime.

It is a super-2 number, since 2×21513256453² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513256459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 110493 + ... + 235021.

It is an arithmetic number, because the mean of its divisors is an integer number (1473625755).

Almost surely, 2^21513256453 is an apocalyptic number.

It is an amenable number.

21513256453 is a deficient number, since it is larger than the sum of its proper divisors (2064755627).

21513256453 is a wasteful number, since it uses less digits than its factorization.

21513256453 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124776.

The product of its digits is 108000, while the sum is 37.

Adding to 21513256453 its reverse (35465231512), we get a palindrome (56978487965).

The spelling of 21513256453 in words is "twenty-one billion, five hundred thirteen million, two hundred fifty-six thousand, four hundred fifty-three".