81553873 has 2 divisors, whose sum is σ = 81553874. Its totient is φ = 81553872.

The previous prime is 81553867. The next prime is 81553877. The reversal of 81553873 is 37835518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73068304 + 8485569 = 8548^2 + 2913^2 .

It is a cyclic number.

It is not a de Polignac number, because 81553873 - 2¹⁷ = 81422801 is a prime.

It is equal to p_4754929 and since 81553873 and 4754929 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81553877) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40776936 + 40776937.

It is an arithmetic number, because the mean of its divisors is an integer number (40776937).

Almost surely, 2^81553873 is an apocalyptic number.

It is an amenable number.

81553873 is a deficient number, since it is larger than the sum of its proper divisors (1).

81553873 is an equidigital number, since it uses as much as digits as its factorization.

81553873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 100800, while the sum is 40.

The square root of 81553873 is about 9030.7182992274. The cubic root of 81553873 is about 433.6588330849.

The spelling of 81553873 in words is "eighty-one million, five hundred fifty-three thousand, eight hundred seventy-three".