81556373 has 2 divisors, whose sum is σ = 81556374. Its totient is φ = 81556372.

The previous prime is 81556331. The next prime is 81556411. The reversal of 81556373 is 37365518.

It is an a-pointer prime, because the next prime (81556411) can be obtained adding 81556373 to its sum of digits (38).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62694724 + 18861649 = 7918^2 + 4343^2 .

It is a cyclic number.

It is not a de Polignac number, because 81556373 - 2⁶ = 81556309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81556313) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40778186 + 40778187.

It is an arithmetic number, because the mean of its divisors is an integer number (40778187).

Almost surely, 2^81556373 is an apocalyptic number.

It is an amenable number.

81556373 is a deficient number, since it is larger than the sum of its proper divisors (1).

81556373 is an equidigital number, since it uses as much as digits as its factorization.

81556373 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 75600, while the sum is 38.

The square root of 81556373 is about 9030.8567146202. The cubic root of 81556373 is about 433.6632642499.

The spelling of 81556373 in words is "eighty-one million, five hundred fifty-six thousand, three hundred seventy-three".