21347231 has 4 divisors (see below), whose sum is σ = 21364872. Its totient is φ = 21329592.

The previous prime is 21347213. The next prime is 21347233. The reversal of 21347231 is 13274312.

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 21347231 - 2¹⁰ = 21346207 is a prime.

It is a super-2 number, since 2×21347231² = 911408542734722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21347197 and 21347206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21347233) 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, 6860 + ... + 9473.

It is an arithmetic number, because the mean of its divisors is an integer number (5341218).

Almost surely, 2^21347231 is an apocalyptic number.

21347231 is a deficient number, since it is larger than the sum of its proper divisors (17641).

21347231 is a wasteful number, since it uses less digits than its factorization.

21347231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17640.

The product of its digits is 1008, while the sum is 23.

The square root of 21347231 is about 4620.3063751228. The cubic root of 21347231 is about 277.4047223161.

The spelling of 21347231 in words is "twenty-one million, three hundred forty-seven thousand, two hundred thirty-one".