21354276721 has 4 divisors (see below), whose sum is σ = 21510147492. Its totient is φ = 21198405952.

The previous prime is 21354276709. The next prime is 21354276737. The reversal of 21354276721 is 12767245312.

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 9382634496 + 11971642225 = 96864^2 + 109415^2 .

It is a cyclic number.

It is not a de Polignac number, because 21354276721 - 2⁵ = 21354276689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21354276781) 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, 77935180 + ... + 77935453.

It is an arithmetic number, because the mean of its divisors is an integer number (5377536873).

Almost surely, 2^21354276721 is an apocalyptic number.

It is an amenable number.

21354276721 is a deficient number, since it is larger than the sum of its proper divisors (155870771).

21354276721 is a wasteful number, since it uses less digits than its factorization.

21354276721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 155870770.

The product of its digits is 141120, while the sum is 40.

The spelling of 21354276721 in words is "twenty-one billion, three hundred fifty-four million, two hundred seventy-six thousand, seven hundred twenty-one".