28991878 has 4 divisors (see below), whose sum is σ = 43487820. Its totient is φ = 14495938.

The previous prime is 28991873. The next prime is 28991923. The reversal of 28991878 is 87819982.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28991873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7247968 + ... + 7247971.

It is an arithmetic number, because the mean of its divisors is an integer number (10871955).

Almost surely, 2^28991878 is an apocalyptic number.

28991878 is a deficient number, since it is larger than the sum of its proper divisors (14495942).

28991878 is a wasteful number, since it uses less digits than its factorization.

28991878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14495941.

The product of its digits is 580608, while the sum is 52.

The square root of 28991878 is about 5384.4106455582. The cubic root of 28991878 is about 307.2029978707.

The spelling of 28991878 in words is "twenty-eight million, nine hundred ninety-one thousand, eight hundred seventy-eight".