20902181 has 2 divisors, whose sum is σ = 20902182. Its totient is φ = 20902180.

The previous prime is 20902177. The next prime is 20902237. The reversal of 20902181 is 18120902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16240900 + 4661281 = 4030^2 + 2159^2 .

It is a cyclic number.

It is not a de Polignac number, because 20902181 - 2² = 20902177 is a prime.

It is a super-2 number, since 2×20902181² = 873802341113522, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20902111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10451090 + 10451091.

It is an arithmetic number, because the mean of its divisors is an integer number (10451091).

Almost surely, 2^20902181 is an apocalyptic number.

It is an amenable number.

20902181 is a deficient number, since it is larger than the sum of its proper divisors (1).

20902181 is an equidigital number, since it uses as much as digits as its factorization.

20902181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 20902181 is about 4571.8903092703. The cubic root of 20902181 is about 275.4633774440.

The spelling of 20902181 in words is "twenty million, nine hundred two thousand, one hundred eighty-one".