21398647 has 2 divisors, whose sum is σ = 21398648. Its totient is φ = 21398646.

The previous prime is 21398623. The next prime is 21398683. The reversal of 21398647 is 74689312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21398647 - 2⁷ = 21398519 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21398687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699323 + 10699324.

It is an arithmetic number, because the mean of its divisors is an integer number (10699324).

Almost surely, 2^21398647 is an apocalyptic number.

21398647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21398647 is an equidigital number, since it uses as much as digits as its factorization.

21398647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72576, while the sum is 40.

The square root of 21398647 is about 4625.8671619492. The cubic root of 21398647 is about 277.6272586783.

The spelling of 21398647 in words is "twenty-one million, three hundred ninety-eight thousand, six hundred forty-seven".