28921788 has 36 divisors (see below), whose sum is σ = 83552560. Its totient is φ = 8263296.

The previous prime is 28921771. The next prime is 28921807. The reversal of 28921788 is 88712982.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×28921788² = 1672939642233888, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 57133 + ... + 57636.

Almost surely, 2^28921788 is an apocalyptic number.

28921788 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

28921788 is an abundant number, since it is smaller than the sum of its proper divisors (54630772).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28921788 is a wasteful number, since it uses less digits than its factorization.

28921788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 114786 (or 114781 counting only the distinct ones).

The product of its digits is 129024, while the sum is 45.

The square root of 28921788 is about 5377.8981024188. The cubic root of 28921788 is about 306.9552361461.

The spelling of 28921788 in words is "twenty-eight million, nine hundred twenty-one thousand, seven hundred eighty-eight".