21702491 has 2 divisors, whose sum is σ = 21702492. Its totient is φ = 21702490.

The previous prime is 21702479. The next prime is 21702517. The reversal of 21702491 is 19420712.

It is an a-pointer prime, because the next prime (21702517) can be obtained adding 21702491 to its sum of digits (26).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21702491 - 2¹⁰ = 21701467 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21702491.

It is not a weakly prime, because it can be changed into another prime (21702431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10851245 + 10851246.

It is an arithmetic number, because the mean of its divisors is an integer number (10851246).

Almost surely, 2^21702491 is an apocalyptic number.

21702491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21702491 is an equidigital number, since it uses as much as digits as its factorization.

21702491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21702491 is about 4658.5932426002. The cubic root of 21702491 is about 278.9351176404.

The spelling of 21702491 in words is "twenty-one million, seven hundred two thousand, four hundred ninety-one".