21056720321 has 8 divisors (see below), whose sum is σ = 25915963584. Its totient is φ = 16660262160.

The previous prime is 21056720291. The next prime is 21056720339. The reversal of 21056720321 is 12302765012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21056720321 - 2⁶ = 21056720257 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21056720351) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 115696175 + ... + 115696356.

It is an arithmetic number, because the mean of its divisors is an integer number (3239495448).

Almost surely, 2^21056720321 is an apocalyptic number.

It is an amenable number.

21056720321 is a deficient number, since it is larger than the sum of its proper divisors (4859243263).

21056720321 is a wasteful number, since it uses less digits than its factorization.

21056720321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231392551.

The product of its (nonzero) digits is 5040, while the sum is 29.

The spelling of 21056720321 in words is "twenty-one billion, fifty-six million, seven hundred twenty thousand, three hundred twenty-one".