21385181 has 2 divisors, whose sum is σ = 21385182. Its totient is φ = 21385180.

The previous prime is 21385163. The next prime is 21385207. The reversal of 21385181 is 18158312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20025625 + 1359556 = 4475^2 + 1166^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21385181 is a prime.

It is a super-2 number, since 2×21385181² = 914651932805522, 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 (21385681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10692590 + 10692591.

It is an arithmetic number, because the mean of its divisors is an integer number (10692591).

Almost surely, 2^21385181 is an apocalyptic number.

It is an amenable number.

21385181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21385181 is an equidigital number, since it uses as much as digits as its factorization.

21385181 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1920, while the sum is 29.

The square root of 21385181 is about 4624.4114220082. The cubic root of 21385181 is about 277.5690102425.

The spelling of 21385181 in words is "twenty-one million, three hundred eighty-five thousand, one hundred eighty-one".