21380391 has 12 divisors (see below), whose sum is σ = 31157568. Its totient is φ = 14126784.

The previous prime is 21380371. The next prime is 21380399. The reversal of 21380391 is 19308312.

It is not a de Polignac number, because 21380391 - 2⁹ = 21379879 is a prime.

It is a super-2 number, since 2×21380391² = 914242238625762, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21380399) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9495 + ... + 11528.

It is an arithmetic number, because the mean of its divisors is an integer number (2596464).

Almost surely, 2^21380391 is an apocalyptic number.

21380391 is a deficient number, since it is larger than the sum of its proper divisors (9777177).

21380391 is a wasteful number, since it uses less digits than its factorization.

21380391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21142 (or 21139 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 21380391 is about 4623.8934892577. The cubic root of 21380391 is about 277.5482847560.

The spelling of 21380391 in words is "twenty-one million, three hundred eighty thousand, three hundred ninety-one".