81287273 has 2 divisors, whose sum is σ = 81287274. Its totient is φ = 81287272.

The previous prime is 81287249. The next prime is 81287279. The reversal of 81287273 is 37278218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 77299264 + 3988009 = 8792^2 + 1997^2 .

It is a cyclic number.

It is not a de Polignac number, because 81287273 - 2¹² = 81283177 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (81287279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40643636 + 40643637.

It is an arithmetic number, because the mean of its divisors is an integer number (40643637).

Almost surely, 2^81287273 is an apocalyptic number.

It is an amenable number.

81287273 is a deficient number, since it is larger than the sum of its proper divisors (1).

81287273 is an equidigital number, since it uses as much as digits as its factorization.

81287273 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37632, while the sum is 38.

The square root of 81287273 is about 9015.9454856382. The cubic root of 81287273 is about 433.1857729663.

The spelling of 81287273 in words is "eighty-one million, two hundred eighty-seven thousand, two hundred seventy-three".