21442723 has 4 divisors (see below), whose sum is σ = 21663880. Its totient is φ = 21221568.

The previous prime is 21442717. The next prime is 21442741. The reversal of 21442723 is 32724412.

It is a happy number.

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 21442723 - 2¹³ = 21434531 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21442703) 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 in 3 ways as a sum of consecutive naturals, for example, 110433 + ... + 110626.

It is an arithmetic number, because the mean of its divisors is an integer number (5415970).

Almost surely, 2^21442723 is an apocalyptic number.

21442723 is a deficient number, since it is larger than the sum of its proper divisors (221157).

21442723 is an equidigital number, since it uses as much as digits as its factorization.

21442723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221156.

The product of its digits is 2688, while the sum is 25.

The square root of 21442723 is about 4630.6287909959. The cubic root of 21442723 is about 277.8177427950.

The spelling of 21442723 in words is "twenty-one million, four hundred forty-two thousand, seven hundred twenty-three".