21631121 has 2 divisors, whose sum is σ = 21631122. Its totient is φ = 21631120.

The previous prime is 21631081. The next prime is 21631171. The reversal of 21631121 is 12113612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20830096 + 801025 = 4564^2 + 895^2 .

It is a cyclic number.

It is not a de Polignac number, because 21631121 - 2¹⁴ = 21614737 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21631121.

It is not a weakly prime, because it can be changed into another prime (21631171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10815560 + 10815561.

It is an arithmetic number, because the mean of its divisors is an integer number (10815561).

Almost surely, 2^21631121 is an apocalyptic number.

It is an amenable number.

21631121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21631121 is an equidigital number, since it uses as much as digits as its factorization.

21631121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72, while the sum is 17.

The square root of 21631121 is about 4650.9268968669. The cubic root of 21631121 is about 278.6290166531.

Adding to 21631121 its reverse (12113612), we get a palindrome (33744733).

The spelling of 21631121 in words is "twenty-one million, six hundred thirty-one thousand, one hundred twenty-one".