21023623 has 2 divisors, whose sum is σ = 21023624. Its totient is φ = 21023622.

The previous prime is 21023599. The next prime is 21023641. The reversal of 21023623 is 32632012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21023623 - 2⁵ = 21023591 is a prime.

It is a super-2 number, since 2×21023623² = 883985448092258, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21023623.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21023663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10511811 + 10511812.

It is an arithmetic number, because the mean of its divisors is an integer number (10511812).

Almost surely, 2^21023623 is an apocalyptic number.

21023623 is a deficient number, since it is larger than the sum of its proper divisors (1).

21023623 is an equidigital number, since it uses as much as digits as its factorization.

21023623 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 19.

The square root of 21023623 is about 4585.1524511187. The cubic root of 21023623 is about 275.9958297697.

Adding to 21023623 its reverse (32632012), we get a palindrome (53655635).

The spelling of 21023623 in words is "twenty-one million, twenty-three thousand, six hundred twenty-three".