21001423 has 4 divisors (see below), whose sum is σ = 21725640. Its totient is φ = 20277208.

The previous prime is 21001417. The next prime is 21001429. The reversal of 21001423 is 32410012.

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

It is an interprime number because it is at equal distance from previous prime (21001417) and next prime (21001429).

It is a cyclic number.

It is not a de Polignac number, because 21001423 - 2⁹ = 21000911 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001429) 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, 362065 + ... + 362122.

It is an arithmetic number, because the mean of its divisors is an integer number (5431410).

Almost surely, 2^21001423 is an apocalyptic number.

21001423 is a deficient number, since it is larger than the sum of its proper divisors (724217).

21001423 is an equidigital number, since it uses as much as digits as its factorization.

21001423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724216.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21001423 is about 4582.7309543546. The cubic root of 21001423 is about 275.8986491626.

Adding to 21001423 its reverse (32410012), we get a palindrome (53411435).

The spelling of 21001423 in words is "twenty-one million, one thousand, four hundred twenty-three".