21738231 has 6 divisors (see below), whose sum is σ = 31399680. Its totient is φ = 14492148.

The previous prime is 21738221. The next prime is 21738239. The reversal of 21738231 is 13283712.

It is not a de Polignac number, because 21738231 - 2⁷ = 21738103 is a prime.

It is a super-2 number, since 2×21738231² = 945101374018722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21738195 and 21738204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21738239) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1207671 + ... + 1207688.

It is an arithmetic number, because the mean of its divisors is an integer number (5233280).

Almost surely, 2^21738231 is an apocalyptic number.

21738231 is a deficient number, since it is larger than the sum of its proper divisors (9661449).

21738231 is a wasteful number, since it uses less digits than its factorization.

21738231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2415365 (or 2415362 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21738231 is about 4662.4275865690. The cubic root of 21738231 is about 279.0881518959.

It can be divided in two parts, 2173 and 8231, that added together give a square (10404 = 102²).

The spelling of 21738231 in words is "twenty-one million, seven hundred thirty-eight thousand, two hundred thirty-one".