21593947 has 2 divisors, whose sum is σ = 21593948. Its totient is φ = 21593946.

The previous prime is 21593917. The next prime is 21593959. The reversal of 21593947 is 74939512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21593947 - 2¹⁵ = 21561179 is a prime.

It is not a weakly prime, because it can be changed into another prime (21593917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10796973 + 10796974.

It is an arithmetic number, because the mean of its divisors is an integer number (10796974).

Almost surely, 2^21593947 is an apocalyptic number.

21593947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21593947 is an equidigital number, since it uses as much as digits as its factorization.

21593947 is an evil number, because the sum of its binary digits is even.

The product of its digits is 68040, while the sum is 40.

The square root of 21593947 is about 4646.9287707044. The cubic root of 21593947 is about 278.4693132001.

The spelling of 21593947 in words is "twenty-one million, five hundred ninety-three thousand, nine hundred forty-seven".