21630231 has 12 divisors (see below), whose sum is σ = 35707152. Its totient is φ = 12360096.

The previous prime is 21630229. The next prime is 21630251. The reversal of 21630231 is 13203612.

21630231 is a `hidden beast` number, since 2 + 1 + 630 + 2 + 31 = 666.

It is not a de Polignac number, because 21630231 - 2¹ = 21630229 is a prime.

It is a super-2 number, since 2×21630231² = 935733786226722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21630211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 171606 + ... + 171731.

It is an arithmetic number, because the mean of its divisors is an integer number (2975596).

Almost surely, 2^21630231 is an apocalyptic number.

21630231 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21630231 is a deficient number, since it is larger than the sum of its proper divisors (14076921).

21630231 is a wasteful number, since it uses less digits than its factorization.

21630231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343350 (or 343347 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 18.

The square root of 21630231 is about 4650.8312160301. The cubic root of 21630231 is about 278.6251952573.

Adding to 21630231 its reverse (13203612), we get a palindrome (34833843).

The spelling of 21630231 in words is "twenty-one million, six hundred thirty thousand, two hundred thirty-one".