21500023 has 2 divisors, whose sum is σ = 21500024. Its totient is φ = 21500022.

The previous prime is 21500021. The next prime is 21500029. The reversal of 21500023 is 32000512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21500023 - 2¹ = 21500021 is a prime.

Together with 21500021, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21499976 and 21500012.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21500021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10750011 + 10750012.

It is an arithmetic number, because the mean of its divisors is an integer number (10750012).

Almost surely, 2^21500023 is an apocalyptic number.

21500023 is a deficient number, since it is larger than the sum of its proper divisors (1).

21500023 is an equidigital number, since it uses as much as digits as its factorization.

21500023 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 60, while the sum is 13.

The square root of 21500023 is about 4636.8117279010. The cubic root of 21500023 is about 278.0649874809.

Adding to 21500023 its reverse (32000512), we get a palindrome (53500535).

The spelling of 21500023 in words is "twenty-one million, five hundred thousand, twenty-three".