21147231 has 16 divisors (see below), whose sum is σ = 32295168. Its totient is φ = 12057600.

The previous prime is 21147229. The next prime is 21147233. The reversal of 21147231 is 13274112.

It is an interprime number because it is at equal distance from previous prime (21147229) and next prime (21147233).

It is not a de Polignac number, because 21147231 - 2¹ = 21147229 is a prime.

It is a super-2 number, since 2×21147231² = 894410757934722, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 21147198 and 21147207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21147233) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12676 + ... + 14246.

It is an arithmetic number, because the mean of its divisors is an integer number (2018448).

Almost surely, 2^21147231 is an apocalyptic number.

21147231 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21147231 is a deficient number, since it is larger than the sum of its proper divisors (11147937).

21147231 is a wasteful number, since it uses less digits than its factorization.

21147231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2222.

The product of its digits is 336, while the sum is 21.

The square root of 21147231 is about 4598.6118557669. The cubic root of 21147231 is about 276.5356772544.

The spelling of 21147231 in words is "twenty-one million, one hundred forty-seven thousand, two hundred thirty-one".