21510433253 has 4 divisors (see below), whose sum is σ = 21647442540. Its totient is φ = 21373423968.

The previous prime is 21510433247. The next prime is 21510433261. The reversal of 21510433253 is 35233401512.

It is a happy number.

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 12316116484 + 9194316769 = 110978^2 + 95887^2 .

It is a cyclic number.

It is not a de Polignac number, because 21510433253 - 2¹⁴ = 21510416869 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21510433453) 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, 68504408 + ... + 68504721.

It is an arithmetic number, because the mean of its divisors is an integer number (5411860635).

Almost surely, 2^21510433253 is an apocalyptic number.

It is an amenable number.

21510433253 is a deficient number, since it is larger than the sum of its proper divisors (137009287).

21510433253 is a wasteful number, since it uses less digits than its factorization.

21510433253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137009286.

The product of its (nonzero) digits is 10800, while the sum is 29.

Adding to 21510433253 its reverse (35233401512), we get a palindrome (56743834765).

The spelling of 21510433253 in words is "twenty-one billion, five hundred ten million, four hundred thirty-three thousand, two hundred fifty-three".