81939373 has 2 divisors, whose sum is σ = 81939374. Its totient is φ = 81939372.

The previous prime is 81939367. The next prime is 81939391. The reversal of 81939373 is 37393918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 74874409 + 7064964 = 8653^2 + 2658^2 .

It is a cyclic number.

It is not a de Polignac number, because 81939373 - 2¹³ = 81931181 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81939313) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40969686 + 40969687.

It is an arithmetic number, because the mean of its divisors is an integer number (40969687).

Almost surely, 2^81939373 is an apocalyptic number.

It is an amenable number.

81939373 is a deficient number, since it is larger than the sum of its proper divisors (1).

81939373 is an equidigital number, since it uses as much as digits as its factorization.

81939373 is an evil number, because the sum of its binary digits is even.

The product of its digits is 122472, while the sum is 43.

The square root of 81939373 is about 9052.0369530841. The cubic root of 81939373 is about 434.3410519024.

The spelling of 81939373 in words is "eighty-one million, nine hundred thirty-nine thousand, three hundred seventy-three".