21871231 has 6 divisors (see below), whose sum is σ = 23233760. Its totient is φ = 20584416.

The previous prime is 21871207. The next prime is 21871237. The reversal of 21871231 is 13217812.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-21871231 is a prime.

It is a super-2 number, since 2×21871231² = 956701490910722, 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 = 21871196 and 21871205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21871237) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 37551 + ... + 38128.

Almost surely, 2^21871231 is an apocalyptic number.

21871231 is a deficient number, since it is larger than the sum of its proper divisors (1362529).

21871231 is an equidigital number, since it uses as much as digits as its factorization.

21871231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75713 (or 75696 counting only the distinct ones).

The product of its digits is 672, while the sum is 25.

The square root of 21871231 is about 4676.6687930620. The cubic root of 21871231 is about 279.6561723554.

The spelling of 21871231 in words is "twenty-one million, eight hundred seventy-one thousand, two hundred thirty-one".