21742493 has 2 divisors, whose sum is σ = 21742494. Its totient is φ = 21742492.

The previous prime is 21742481. The next prime is 21742571. The reversal of 21742493 is 39424712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13227769 + 8514724 = 3637^2 + 2918^2 .

It is a cyclic number.

It is not a de Polignac number, because 21742493 - 2¹⁰ = 21741469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21742793) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10871246 + 10871247.

It is an arithmetic number, because the mean of its divisors is an integer number (10871247).

Almost surely, 2^21742493 is an apocalyptic number.

It is an amenable number.

21742493 is a deficient number, since it is larger than the sum of its proper divisors (1).

21742493 is an equidigital number, since it uses as much as digits as its factorization.

21742493 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 32.

The square root of 21742493 is about 4662.8846222054. The cubic root of 21742493 is about 279.1063900555.

The spelling of 21742493 in words is "twenty-one million, seven hundred forty-two thousand, four hundred ninety-three".