21139823 has 8 divisors (see below), whose sum is σ = 22602528. Its totient is φ = 19701504.

The previous prime is 21139813. The next prime is 21139831. The reversal of 21139823 is 32893112.

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

It is not a de Polignac number, because 21139823 - 2¹⁸ = 20877679 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 (21139813) 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, 4286 + ... + 7787.

It is an arithmetic number, because the mean of its divisors is an integer number (2825316).

Almost surely, 2^21139823 is an apocalyptic number.

21139823 is a deficient number, since it is larger than the sum of its proper divisors (1462705).

21139823 is a wasteful number, since it uses less digits than its factorization.

21139823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12193.

The product of its digits is 2592, while the sum is 29.

The square root of 21139823 is about 4597.8063247597. The cubic root of 21139823 is about 276.5033827891.

The spelling of 21139823 in words is "twenty-one million, one hundred thirty-nine thousand, eight hundred twenty-three".