91639209 has 8 divisors (see below), whose sum is σ = 122387392. Its totient is φ = 60991920.

The previous prime is 91639189. The next prime is 91639241. The reversal of 91639209 is 90293619.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 91639209 - 2¹² = 91635113 is a prime.

It is a super-2 number, since 2×91639209² = 16795489252291362, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (91632209) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23077 + ... + 26754.

It is an arithmetic number, because the mean of its divisors is an integer number (15298424).

Almost surely, 2^91639209 is an apocalyptic number.

It is an amenable number.

91639209 is a deficient number, since it is larger than the sum of its proper divisors (30748183).

91639209 is a wasteful number, since it uses less digits than its factorization.

91639209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50447.

The product of its (nonzero) digits is 26244, while the sum is 39.

The square root of 91639209 is about 9572.8370402927. The cubic root of 91639209 is about 450.8448474260.

The spelling of 91639209 in words is "ninety-one million, six hundred thirty-nine thousand, two hundred nine".