81910013 has 2 divisors, whose sum is σ = 81910014. Its totient is φ = 81910012.

The previous prime is 81909983. The next prime is 81910027. The reversal of 81910013 is 31001918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 41434969 + 40475044 = 6437^2 + 6362^2 .

It is a cyclic number.

It is not a de Polignac number, because 81910013 - 2¹⁰ = 81908989 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81910033) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40955006 + 40955007.

It is an arithmetic number, because the mean of its divisors is an integer number (40955007).

Almost surely, 2^81910013 is an apocalyptic number.

It is an amenable number.

81910013 is a deficient number, since it is larger than the sum of its proper divisors (1).

81910013 is an equidigital number, since it uses as much as digits as its factorization.

81910013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 23.

The square root of 81910013 is about 9050.4150733544. The cubic root of 81910013 is about 434.2891689218.

The spelling of 81910013 in words is "eighty-one million, nine hundred ten thousand, thirteen".