21390993351 has 64 divisors (see below), whose sum is σ = 39179427840. Its totient is φ = 11232276480.

The previous prime is 21390993317. The next prime is 21390993353. The reversal of 21390993351 is 15339909312.

It is a happy number.

It is not a de Polignac number, because 21390993351 - 2⁶ = 21390993287 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21390993297 and 21390993306.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390993353) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 528391 + ... + 567431.

It is an arithmetic number, because the mean of its divisors is an integer number (612178560).

Almost surely, 2^21390993351 is an apocalyptic number.

21390993351 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21390993351 is a deficient number, since it is larger than the sum of its proper divisors (17788434489).

21390993351 is a wasteful number, since it uses less digits than its factorization.

21390993351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39293 (or 39287 counting only the distinct ones).

The product of its (nonzero) digits is 196830, while the sum is 45.

The spelling of 21390993351 in words is "twenty-one billion, three hundred ninety million, nine hundred ninety-three thousand, three hundred fifty-one".