72102809 has 2 divisors, whose sum is σ = 72102810. Its totient is φ = 72102808.

The previous prime is 72102803. The next prime is 72102839. The reversal of 72102809 is 90820127.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 71995225 + 107584 = 8485^2 + 328^2 .

It is a cyclic number.

It is not a de Polignac number, because 72102809 - 2¹² = 72098713 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 (72102803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36051404 + 36051405.

It is an arithmetic number, because the mean of its divisors is an integer number (36051405).

Almost surely, 2^72102809 is an apocalyptic number.

It is an amenable number.

72102809 is a deficient number, since it is larger than the sum of its proper divisors (1).

72102809 is an equidigital number, since it uses as much as digits as its factorization.

72102809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 29.

The square root of 72102809 is about 8491.3372916167. The cubic root of 72102809 is about 416.2146809364.

The spelling of 72102809 in words is "seventy-two million, one hundred two thousand, eight hundred nine".