21731161 has 2 divisors, whose sum is σ = 21731162. Its totient is φ = 21731160.

The previous prime is 21731147. The next prime is 21731191. The reversal of 21731161 is 16113712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16974400 + 4756761 = 4120^2 + 2181^2 .

It is a cyclic number.

It is not a de Polignac number, because 21731161 - 2⁹ = 21730649 is a prime.

It is a Chen prime.

It is a zygodrome in base 3.

It is not a weakly prime, because it can be changed into another prime (21731111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10865580 + 10865581.

It is an arithmetic number, because the mean of its divisors is an integer number (10865581).

Almost surely, 2^21731161 is an apocalyptic number.

It is an amenable number.

21731161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21731161 is an equidigital number, since it uses as much as digits as its factorization.

21731161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 252, while the sum is 22.

The square root of 21731161 is about 4661.6693361928. The cubic root of 21731161 is about 279.0578923471.

Adding to 21731161 its reverse (16113712), we get a palindrome (37844873).

The spelling of 21731161 in words is "twenty-one million, seven hundred thirty-one thousand, one hundred sixty-one".