21981423 has 8 divisors (see below), whose sum is σ = 30851200. Its totient is φ = 13882968.

The previous prime is 21981419. The next prime is 21981433. The reversal of 21981423 is 32418912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21981423 - 2² = 21981419 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981403) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 192763 + ... + 192876.

It is an arithmetic number, because the mean of its divisors is an integer number (3856400).

Almost surely, 2^21981423 is an apocalyptic number.

21981423 is a deficient number, since it is larger than the sum of its proper divisors (8869777).

21981423 is a wasteful number, since it uses less digits than its factorization.

21981423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 385661.

The product of its digits is 3456, while the sum is 30.

The square root of 21981423 is about 4688.4350267440. The cubic root of 21981423 is about 280.1250419398.

The spelling of 21981423 in words is "twenty-one million, nine hundred eighty-one thousand, four hundred twenty-three".