21990523 has 2 divisors, whose sum is σ = 21990524. Its totient is φ = 21990522.

The previous prime is 21990517. The next prime is 21990541. The reversal of 21990523 is 32509912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21990523 - 2⁵ = 21990491 is a prime.

It is not a weakly prime, because it can be changed into another prime (21990623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10995261 + 10995262.

It is an arithmetic number, because the mean of its divisors is an integer number (10995262).

Almost surely, 2^21990523 is an apocalyptic number.

21990523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21990523 is an equidigital number, since it uses as much as digits as its factorization.

21990523 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4860, while the sum is 31.

The square root of 21990523 is about 4689.4053994083. The cubic root of 21990523 is about 280.1636925493.

The spelling of 21990523 in words is "twenty-one million, nine hundred ninety thousand, five hundred twenty-three".