21121315253 has 4 divisors (see below), whose sum is σ = 22363745580. Its totient is φ = 19878884928.

The previous prime is 21121315217. The next prime is 21121315277. The reversal of 21121315253 is 35251312112.

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 11465698084 + 9655617169 = 107078^2 + 98263^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121315253 - 2²² = 21117120949 is a prime.

It is a super-2 number, since 2×21121315253² (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 (21121315153) 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, 621215138 + ... + 621215171.

It is an arithmetic number, because the mean of its divisors is an integer number (5590936395).

Almost surely, 2^21121315253 is an apocalyptic number.

It is an amenable number.

21121315253 is a deficient number, since it is larger than the sum of its proper divisors (1242430327).

21121315253 is a wasteful number, since it uses less digits than its factorization.

21121315253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1242430326.

The product of its digits is 1800, while the sum is 26.

Adding to 21121315253 its reverse (35251312112), we get a palindrome (56372627365).

The spelling of 21121315253 in words is "twenty-one billion, one hundred twenty-one million, three hundred fifteen thousand, two hundred fifty-three".