21713491 has 2 divisors, whose sum is σ = 21713492. Its totient is φ = 21713490.

The previous prime is 21713479. The next prime is 21713501. The reversal of 21713491 is 19431712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21713491 - 2²¹ = 19616339 is a prime.

It is not a weakly prime, because it can be changed into another prime (21719491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10856745 + 10856746.

It is an arithmetic number, because the mean of its divisors is an integer number (10856746).

Almost surely, 2^21713491 is an apocalyptic number.

21713491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21713491 is an equidigital number, since it uses as much as digits as its factorization.

21713491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1512, while the sum is 28.

The square root of 21713491 is about 4659.7737069519. The cubic root of 21713491 is about 278.9822361647.

The spelling of 21713491 in words is "twenty-one million, seven hundred thirteen thousand, four hundred ninety-one".