81909953 has 2 divisors, whose sum is σ = 81909954. Its totient is φ = 81909952.

The previous prime is 81909943. The next prime is 81909959. The reversal of 81909953 is 35990918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81577024 + 332929 = 9032^2 + 577^2 .

It is a cyclic number.

It is not a de Polignac number, because 81909953 - 2¹⁴ = 81893569 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 (81909959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40954976 + 40954977.

It is an arithmetic number, because the mean of its divisors is an integer number (40954977).

Almost surely, 2^81909953 is an apocalyptic number.

It is an amenable number.

81909953 is a deficient number, since it is larger than the sum of its proper divisors (1).

81909953 is an equidigital number, since it uses as much as digits as its factorization.

81909953 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 87480, while the sum is 44.

The square root of 81909953 is about 9050.4117585887. The cubic root of 81909953 is about 434.2890628812.

The spelling of 81909953 in words is "eighty-one million, nine hundred nine thousand, nine hundred fifty-three".