81555449 has 2 divisors, whose sum is σ = 81555450. Its totient is φ = 81555448.

The previous prime is 81555433. The next prime is 81555457. The reversal of 81555449 is 94455518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 56355049 + 25200400 = 7507^2 + 5020^2 .

It is a cyclic number.

It is not a de Polignac number, because 81555449 - 2⁴ = 81555433 is a prime.

It is not a weakly prime, because it can be changed into another prime (81555469) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40777724 + 40777725.

It is an arithmetic number, because the mean of its divisors is an integer number (40777725).

Almost surely, 2^81555449 is an apocalyptic number.

It is an amenable number.

81555449 is a deficient number, since it is larger than the sum of its proper divisors (1).

81555449 is an equidigital number, since it uses as much as digits as its factorization.

81555449 is an evil number, because the sum of its binary digits is even.

The product of its digits is 144000, while the sum is 41.

The square root of 81555449 is about 9030.8055565381. The cubic root of 81555449 is about 433.6616265018.

The spelling of 81555449 in words is "eighty-one million, five hundred fifty-five thousand, four hundred forty-nine".