21631801 has 3 divisors (see below), whose sum is σ = 21636453. Its totient is φ = 21627150.

The previous prime is 21631777. The next prime is 21631817. The reversal of 21631801 is 10813612.

The square root of 21631801 is 4651.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 21631801 - 2⁹ = 21631289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21631301) 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 2 ways as a sum of consecutive naturals, for example, 2326 + ... + 6976.

It is an arithmetic number, because the mean of its divisors is an integer number (7212151).

Almost surely, 2^21631801 is an apocalyptic number.

21631801 is the 4651-st square number.

21631801 is the 2326-th centered octagonal number.

It is an amenable number.

21631801 is a deficient number, since it is larger than the sum of its proper divisors (4652).

21631801 is an frugal number, since it uses more digits than its factorization.

21631801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9302 (or 4651 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 22.

The cubic root of 21631801 is about 278.6319363006.

The spelling of 21631801 in words is "twenty-one million, six hundred thirty-one thousand, eight hundred one".