21083378621 has 4 divisors (see below), whose sum is σ = 21086364000. Its totient is φ = 21080393244.

The previous prime is 21083378609. The next prime is 21083378629. The reversal of 21083378621 is 12687338012.

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 a de Polignac number, because none of the positive numbers 2^k-21083378621 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 (21083378629) 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, 1482071 + ... + 1496228.

It is an arithmetic number, because the mean of its divisors is an integer number (5271591000).

Almost surely, 2^21083378621 is an apocalyptic number.

It is an amenable number.

21083378621 is a deficient number, since it is larger than the sum of its proper divisors (2985379).

21083378621 is an equidigital number, since it uses as much as digits as its factorization.

21083378621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2985378.

The product of its (nonzero) digits is 96768, while the sum is 41.

The spelling of 21083378621 in words is "twenty-one billion, eighty-three million, three hundred seventy-eight thousand, six hundred twenty-one".