21372256309 has 4 divisors (see below), whose sum is σ = 21379329216. Its totient is φ = 21365183404.

The previous prime is 21372256289. The next prime is 21372256429. The reversal of 21372256309 is 90365227312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21372256309 - 2⁹ = 21372255797 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 (21372256109) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3531919 + ... + 3537964.

It is an arithmetic number, because the mean of its divisors is an integer number (5344832304).

Almost surely, 2^21372256309 is an apocalyptic number.

It is an amenable number.

21372256309 is a deficient number, since it is larger than the sum of its proper divisors (7072907).

21372256309 is an equidigital number, since it uses as much as digits as its factorization.

21372256309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7072906.

The product of its (nonzero) digits is 136080, while the sum is 40.

The spelling of 21372256309 in words is "twenty-one billion, three hundred seventy-two million, two hundred fifty-six thousand, three hundred nine".