21718351 has 2 divisors, whose sum is σ = 21718352. Its totient is φ = 21718350.

The previous prime is 21718327. The next prime is 21718363. The reversal of 21718351 is 15381712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21718351 - 2¹³ = 21710159 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21718381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10859175 + 10859176.

It is an arithmetic number, because the mean of its divisors is an integer number (10859176).

Almost surely, 2^21718351 is an apocalyptic number.

21718351 is a deficient number, since it is larger than the sum of its proper divisors (1).

21718351 is an equidigital number, since it uses as much as digits as its factorization.

21718351 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 28.

The square root of 21718351 is about 4660.2951623261. The cubic root of 21718351 is about 279.0030489169.

The spelling of 21718351 in words is "twenty-one million, seven hundred eighteen thousand, three hundred fifty-one".