21274151621 has 4 divisors (see below), whose sum is σ = 21280096044. Its totient is φ = 21268207200.

The previous prime is 21274151539. The next prime is 21274151623. The reversal of 21274151621 is 12615147212.

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 19026064225 + 2248087396 = 137935^2 + 47414^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21274151621 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 (21274151623) 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, 2966840 + ... + 2974001.

It is an arithmetic number, because the mean of its divisors is an integer number (5320024011).

Almost surely, 2^21274151621 is an apocalyptic number.

It is an amenable number.

21274151621 is a deficient number, since it is larger than the sum of its proper divisors (5944423).

21274151621 is an equidigital number, since it uses as much as digits as its factorization.

21274151621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5944422.

The product of its digits is 6720, while the sum is 32.

Adding to 21274151621 its reverse (12615147212), we get a palindrome (33889298833).

The spelling of 21274151621 in words is "twenty-one billion, two hundred seventy-four million, one hundred fifty-one thousand, six hundred twenty-one".