21293647 has 2 divisors, whose sum is σ = 21293648. Its totient is φ = 21293646.

The previous prime is 21293633. The next prime is 21293659. The reversal of 21293647 is 74639212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21293647 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21293347) 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 as a sum of consecutive naturals, namely, 10646823 + 10646824.

It is an arithmetic number, because the mean of its divisors is an integer number (10646824).

Almost surely, 2^21293647 is an apocalyptic number.

21293647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21293647 is an equidigital number, since it uses as much as digits as its factorization.

21293647 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18144, while the sum is 34.

The square root of 21293647 is about 4614.5039820115. The cubic root of 21293647 is about 277.1724219430.

It can be divided in two parts, 2129 and 3647, that added together give a square (5776 = 76²).

The spelling of 21293647 in words is "twenty-one million, two hundred ninety-three thousand, six hundred forty-seven".