21372656209 has 4 divisors (see below), whose sum is σ = 21950295604. Its totient is φ = 20795016816.

The previous prime is 21372656203. The next prime is 21372656219. The reversal of 21372656209 is 90265627312.

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 17614598400 + 3758057809 = 132720^2 + 61303^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21372656209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21372656203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 288819642 + ... + 288819715.

It is an arithmetic number, because the mean of its divisors is an integer number (5487573901).

Almost surely, 2^21372656209 is an apocalyptic number.

It is an amenable number.

21372656209 is a deficient number, since it is larger than the sum of its proper divisors (577639395).

21372656209 is an equidigital number, since it uses as much as digits as its factorization.

21372656209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 577639394.

The product of its (nonzero) digits is 272160, while the sum is 43.

The spelling of 21372656209 in words is "twenty-one billion, three hundred seventy-two million, six hundred fifty-six thousand, two hundred nine".