28938991 has 4 divisors (see below), whose sum is σ = 30197232. Its totient is φ = 27680752.

The previous prime is 28938953. The next prime is 28939003. The reversal of 28938991 is 19983982.

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 28938991 - 2¹³ = 28930799 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28938911) 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, 629086 + ... + 629131.

It is an arithmetic number, because the mean of its divisors is an integer number (7549308).

Almost surely, 2^28938991 is an apocalyptic number.

28938991 is a deficient number, since it is larger than the sum of its proper divisors (1258241).

28938991 is a wasteful number, since it uses less digits than its factorization.

28938991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1258240.

The product of its digits is 279936, while the sum is 49.

The square root of 28938991 is about 5379.4972813452. The cubic root of 28938991 is about 307.0160842086.

It can be divided in two parts, 28938 and 991, that added together give a square (29929 = 173²).

The spelling of 28938991 in words is "twenty-eight million, nine hundred thirty-eight thousand, nine hundred ninety-one".