81170213 has 2 divisors, whose sum is σ = 81170214. Its totient is φ = 81170212.

The previous prime is 81170161. The next prime is 81170231. The reversal of 81170213 is 31207118.

It is a happy number.

Together with next prime (81170231) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58721569 + 22448644 = 7663^2 + 4738^2 .

It is a cyclic number.

It is not a de Polignac number, because 81170213 - 2¹² = 81166117 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81170263) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40585106 + 40585107.

It is an arithmetic number, because the mean of its divisors is an integer number (40585107).

Almost surely, 2^81170213 is an apocalyptic number.

It is an amenable number.

81170213 is a deficient number, since it is larger than the sum of its proper divisors (1).

81170213 is an equidigital number, since it uses as much as digits as its factorization.

81170213 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 81170213 is about 9009.4513151468. The cubic root of 81170213 is about 432.9777326597.

The spelling of 81170213 in words is "eighty-one million, one hundred seventy thousand, two hundred thirteen".