21380399 has 2 divisors, whose sum is σ = 21380400. Its totient is φ = 21380398.

The previous prime is 21380371. The next prime is 21380423. The reversal of 21380399 is 99308312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21380399 - 2⁸ = 21380143 is a prime.

It is a super-2 number, since 2×21380399² = 914242922798402, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21380309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10690199 + 10690200.

It is an arithmetic number, because the mean of its divisors is an integer number (10690200).

Almost surely, 2^21380399 is an apocalyptic number.

21380399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21380399 is an equidigital number, since it uses as much as digits as its factorization.

21380399 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 21380399 is about 4623.8943543295. The cubic root of 21380399 is about 277.5483193732.

The spelling of 21380399 in words is "twenty-one million, three hundred eighty thousand, three hundred ninety-nine".