28991707 has 4 divisors (see below), whose sum is σ = 30252240. Its totient is φ = 27731176.

The previous prime is 28991659. The next prime is 28991723. The reversal of 28991707 is 70719982.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 70719982 = 2 ⋅35359991.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28991707 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28991737) 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, 630232 + ... + 630277.

It is an arithmetic number, because the mean of its divisors is an integer number (7563060).

Almost surely, 2^28991707 is an apocalyptic number.

28991707 is a deficient number, since it is larger than the sum of its proper divisors (1260533).

28991707 is a wasteful number, since it uses less digits than its factorization.

28991707 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1260532.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 28991707 is about 5384.3947663595. The cubic root of 28991707 is about 307.2023938876.

The spelling of 28991707 in words is "twenty-eight million, nine hundred ninety-one thousand, seven hundred seven".