21402523 has 2 divisors, whose sum is σ = 21402524. Its totient is φ = 21402522.

The previous prime is 21402517. The next prime is 21402527. The reversal of 21402523 is 32520412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21402523 - 2¹⁷ = 21271451 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21402523.

It is not a weakly prime, because it can be changed into another prime (21402527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701261 + 10701262.

It is an arithmetic number, because the mean of its divisors is an integer number (10701262).

Almost surely, 2^21402523 is an apocalyptic number.

21402523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21402523 is an equidigital number, since it uses as much as digits as its factorization.

21402523 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21402523 is about 4626.2860914561. The cubic root of 21402523 is about 277.6440201476.

Adding to 21402523 its reverse (32520412), we get a palindrome (53922935).

The spelling of 21402523 in words is "twenty-one million, four hundred two thousand, five hundred twenty-three".