21631290 has 16 divisors (see below), whose sum is σ = 51915168. Its totient is φ = 5768336.

The previous prime is 21631289. The next prime is 21631297. The reversal of 21631290 is 9213612.

It is a Curzon number.

It is a plaindrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 21631290.

It is not an unprimeable number, because it can be changed into a prime (21631297) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 360492 + ... + 360551.

It is an arithmetic number, because the mean of its divisors is an integer number (3244698).

Almost surely, 2^21631290 is an apocalyptic number.

21631290 is an abundant number, since it is smaller than the sum of its proper divisors (30283878).

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

21631290 is a wasteful number, since it uses less digits than its factorization.

21631290 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 721053.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 21631290 is about 4650.9450652529. The cubic root of 21631290 is about 278.6297422771.

The spelling of 21631290 in words is "twenty-one million, six hundred thirty-one thousand, two hundred ninety".