21630023 has 4 divisors (see below), whose sum is σ = 21674568. Its totient is φ = 21585480.

The previous prime is 21630019. The next prime is 21630031. The reversal of 21630023 is 32003612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21630023 - 2² = 21630019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21629983 and 21630010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21630013) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21536 + ... + 22517.

It is an arithmetic number, because the mean of its divisors is an integer number (5418642).

Almost surely, 2^21630023 is an apocalyptic number.

21630023 is a deficient number, since it is larger than the sum of its proper divisors (44545).

21630023 is an equidigital number, since it uses as much as digits as its factorization.

21630023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44544.

The product of its (nonzero) digits is 216, while the sum is 17.

The square root of 21630023 is about 4650.8088543822. The cubic root of 21630023 is about 278.6243021519.

Adding to 21630023 its reverse (32003612), we get a palindrome (53633635).

The spelling of 21630023 in words is "twenty-one million, six hundred thirty thousand, twenty-three".