21523399 has 2 divisors, whose sum is σ = 21523400. Its totient is φ = 21523398.

The previous prime is 21523391. The next prime is 21523417. The reversal of 21523399 is 99332512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21523399 - 2³ = 21523391 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21523391) 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, 10761699 + 10761700.

It is an arithmetic number, because the mean of its divisors is an integer number (10761700).

Almost surely, 2^21523399 is an apocalyptic number.

21523399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21523399 is an equidigital number, since it uses as much as digits as its factorization.

21523399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14580, while the sum is 34.

The square root of 21523399 is about 4639.3317406713. The cubic root of 21523399 is about 278.1657267970.

The spelling of 21523399 in words is "twenty-one million, five hundred twenty-three thousand, three hundred ninety-nine".