21159181 has 2 divisors, whose sum is σ = 21159182. Its totient is φ = 21159180.

The previous prime is 21159163. The next prime is 21159211. The reversal of 21159181 is 18195112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20331081 + 828100 = 4509^2 + 910^2 .

It is a cyclic number.

It is not a de Polignac number, because 21159181 - 2¹³ = 21150989 is a prime.

It is a super-2 number, since 2×21159181² = 895421881181522, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21159121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10579590 + 10579591.

It is an arithmetic number, because the mean of its divisors is an integer number (10579591).

Almost surely, 2^21159181 is an apocalyptic number.

It is an amenable number.

21159181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21159181 is an equidigital number, since it uses as much as digits as its factorization.

21159181 is an evil number, because the sum of its binary digits is even.

The product of its digits is 720, while the sum is 28.

The square root of 21159181 is about 4599.9109773995. The cubic root of 21159181 is about 276.5877562409.

The spelling of 21159181 in words is "twenty-one million, one hundred fifty-nine thousand, one hundred eighty-one".