81502209 has 12 divisors (see below), whose sum is σ = 121785300. Its totient is φ = 52461024.

The previous prime is 81502189. The next prime is 81502247. The reversal of 81502209 is 90220518.

It can be written as a sum of positive squares in 2 ways, for example, as 21594609 + 59907600 = 4647^2 + 7740^2 .

It is not a de Polignac number, because 81502209 - 2⁷ = 81502081 is a prime.

It is a super-2 number, since 2×81502209² = 13285220143759362, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81501209) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 155874 + ... + 156395.

It is an arithmetic number, because the mean of its divisors is an integer number (10148775).

Almost surely, 2^81502209 is an apocalyptic number.

It is an amenable number.

81502209 is a deficient number, since it is larger than the sum of its proper divisors (40283091).

81502209 is a wasteful number, since it uses less digits than its factorization.

81502209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 312304 (or 312301 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 81502209 is about 9027.8573869994. The cubic root of 81502209 is about 433.5672401216.

The spelling of 81502209 in words is "eighty-one million, five hundred two thousand, two hundred nine".