21678850021 has 4 divisors (see below), whose sum is σ = 21680268544. Its totient is φ = 21677431500.

The previous prime is 21678850013. The next prime is 21678850051. The reversal of 21678850021 is 12005887612.

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 21678850021 - 2³ = 21678850013 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 (21678850051) 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, 686085 + ... + 716986.

It is an arithmetic number, because the mean of its divisors is an integer number (5420067136).

Almost surely, 2^21678850021 is an apocalyptic number.

It is an amenable number.

21678850021 is a deficient number, since it is larger than the sum of its proper divisors (1418523).

21678850021 is a wasteful number, since it uses less digits than its factorization.

21678850021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1418522.

The product of its (nonzero) digits is 53760, while the sum is 40.

The spelling of 21678850021 in words is "twenty-one billion, six hundred seventy-eight million, eight hundred fifty thousand, twenty-one".