21420623 has 4 divisors (see below), whose sum is σ = 24480720. Its totient is φ = 18360528.

The previous prime is 21420587. The next prime is 21420643. The reversal of 21420623 is 32602412.

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 21420623 - 2²⁴ = 4643407 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21420595 and 21420604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420643) 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, 1530038 + ... + 1530051.

It is an arithmetic number, because the mean of its divisors is an integer number (6120180).

Almost surely, 2^21420623 is an apocalyptic number.

21420623 is a deficient number, since it is larger than the sum of its proper divisors (3060097).

21420623 is an equidigital number, since it uses as much as digits as its factorization.

21420623 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3060096.

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21420623 is about 4628.2418908264. The cubic root of 21420623 is about 277.7222654521.

The spelling of 21420623 in words is "twenty-one million, four hundred twenty thousand, six hundred twenty-three".