21631266 has 16 divisors (see below), whose sum is σ = 48069600. Its totient is φ = 7210404.

The previous prime is 21631243. The next prime is 21631283. The reversal of 21631266 is 66213612.

21631266 is a `hidden beast` number, since 2 + 1 + 631 + 26 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 200236 + ... + 200343.

It is an arithmetic number, because the mean of its divisors is an integer number (3004350).

Almost surely, 2^21631266 is an apocalyptic number.

21631266 is an abundant number, since it is smaller than the sum of its proper divisors (26438334).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21631266 is a wasteful number, since it uses less digits than its factorization.

21631266 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400590 (or 400584 counting only the distinct ones).

The product of its digits is 2592, while the sum is 27.

The square root of 21631266 is about 4650.9424851314. The cubic root of 21631266 is about 278.6296392301.

Adding to 21631266 its reverse (66213612), we get a palindrome (87844878).

The spelling of 21631266 in words is "twenty-one million, six hundred thirty-one thousand, two hundred sixty-six".