21391711 has 6 divisors (see below), whose sum is σ = 23513336. Its totient is φ = 19446900.

The previous prime is 21391703. The next prime is 21391723. The reversal of 21391711 is 11719312.

It is not a de Polignac number, because 21391711 - 2³ = 21391703 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391751) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 88275 + ... + 88516.

Almost surely, 2^21391711 is an apocalyptic number.

21391711 is a deficient number, since it is larger than the sum of its proper divisors (2121625).

21391711 is a wasteful number, since it uses less digits than its factorization.

21391711 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176813 (or 176802 counting only the distinct ones).

The product of its digits is 378, while the sum is 25.

The square root of 21391711 is about 4625.1174039153. The cubic root of 21391711 is about 277.5972594178.

The spelling of 21391711 in words is "twenty-one million, three hundred ninety-one thousand, seven hundred eleven".