213891809 has 2 divisors, whose sum is σ = 213891810. Its totient is φ = 213891808.

The previous prime is 213891781. The next prime is 213891817. The reversal of 213891809 is 908198312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 211557025 + 2334784 = 14545^2 + 1528^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-213891809 is a prime.

It is not a weakly prime, because it can be changed into another prime (213891889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106945904 + 106945905.

It is an arithmetic number, because the mean of its divisors is an integer number (106945905).

Almost surely, 2^213891809 is an apocalyptic number.

It is an amenable number.

213891809 is a deficient number, since it is larger than the sum of its proper divisors (1).

213891809 is an equidigital number, since it uses as much as digits as its factorization.

213891809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 41.

The square root of 213891809 is about 14625.0404785765. The cubic root of 213891809 is about 598.0415859418.

The spelling of 213891809 in words is "two hundred thirteen million, eight hundred ninety-one thousand, eight hundred nine".