21387319 has 2 divisors, whose sum is σ = 21387320. Its totient is φ = 21387318.

The previous prime is 21387313. The next prime is 21387329. The reversal of 21387319 is 91378312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21387319 - 2⁵ = 21387287 is a prime.

It is a super-2 number, since 2×21387319² = 914834828015522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21387313) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10693659 + 10693660.

It is an arithmetic number, because the mean of its divisors is an integer number (10693660).

Almost surely, 2^21387319 is an apocalyptic number.

21387319 is a deficient number, since it is larger than the sum of its proper divisors (1).

21387319 is an equidigital number, since it uses as much as digits as its factorization.

21387319 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 34.

The square root of 21387319 is about 4624.6425807839. The cubic root of 21387319 is about 277.5782599930.

The spelling of 21387319 in words is "twenty-one million, three hundred eighty-seven thousand, three hundred nineteen".