21017990051 has 4 divisors (see below), whose sum is σ = 21080358312. Its totient is φ = 20955621792.

The previous prime is 21017990047. The next prime is 21017990083. The reversal of 21017990051 is 15009971012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21017990051 - 2² = 21017990047 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21017989993 and 21017990020.

It is not an unprimeable number, because it can be changed into a prime (21017990041) 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, 31183625 + ... + 31184298.

It is an arithmetic number, because the mean of its divisors is an integer number (5270089578).

Almost surely, 2^21017990051 is an apocalyptic number.

21017990051 is a deficient number, since it is larger than the sum of its proper divisors (62368261).

21017990051 is an equidigital number, since it uses as much as digits as its factorization.

21017990051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62368260.

The product of its (nonzero) digits is 5670, while the sum is 35.

The spelling of 21017990051 in words is "twenty-one billion, seventeen million, nine hundred ninety thousand, fifty-one".