21253835213 has 4 divisors (see below), whose sum is σ = 22888745628. Its totient is φ = 19618924800.

The previous prime is 21253835179. The next prime is 21253835237. The reversal of 21253835213 is 31253835212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10982620804 + 10271214409 = 104798^2 + 101347^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253835213 - 2²⁶ = 21186726349 is a prime.

It is a super-2 number, since 2×21253835213² (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 (21253835243) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 817455188 + ... + 817455213.

It is an arithmetic number, because the mean of its divisors is an integer number (5722186407).

Almost surely, 2^21253835213 is an apocalyptic number.

It is an amenable number.

21253835213 is a deficient number, since it is larger than the sum of its proper divisors (1634910415).

21253835213 is a wasteful number, since it uses less digits than its factorization.

21253835213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1634910414.

The product of its digits is 43200, while the sum is 35.

Subtracting 21253835213 from its reverse (31253835212), we obtain a palindrome (9999999999).

The spelling of 21253835213 in words is "twenty-one billion, two hundred fifty-three million, eight hundred thirty-five thousand, two hundred thirteen".