82509991 has 4 divisors (see below), whose sum is σ = 84428872. Its totient is φ = 80591112.

The previous prime is 82509967. The next prime is 82509997. The reversal of 82509991 is 19990528.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 82509991 - 2¹⁵ = 82477223 is a prime.

It is a super-2 number, since 2×82509991² = 13615797229640162, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (43), and also a Moran number because the ratio is a prime number: 1918837 = 82509991 / (8 + 2 + 5 + 0 + 9 + 9 + 9 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (82509997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 959376 + ... + 959461.

It is an arithmetic number, because the mean of its divisors is an integer number (21107218).

Almost surely, 2^82509991 is an apocalyptic number.

82509991 is a deficient number, since it is larger than the sum of its proper divisors (1918881).

82509991 is a wasteful number, since it uses less digits than its factorization.

82509991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1918880.

The product of its (nonzero) digits is 58320, while the sum is 43.

The square root of 82509991 is about 9083.5010320911. The cubic root of 82509991 is about 435.3469570852.

The spelling of 82509991 in words is "eighty-two million, five hundred nine thousand, nine hundred ninety-one".