28291978 has 72 divisors (see below), whose sum is σ = 55603044. Its totient is φ = 10686720.

The previous prime is 28291973. The next prime is 28291999. The reversal of 28291978 is 87919282.

It can be written as a sum of positive squares in 2 ways, for example, as 28227969 + 64009 = 5313^2 + 253^2 .

It is a Harshad number since it is a multiple of its sum of digits (46).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28291973) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1230075 + ... + 1230097.

Almost surely, 2^28291978 is an apocalyptic number.

28291978 is a deficient number, since it is larger than the sum of its proper divisors (27311066).

28291978 is a wasteful number, since it uses less digits than its factorization.

28291978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100 (or 66 counting only the distinct ones).

The product of its digits is 145152, while the sum is 46.

The square root of 28291978 is about 5319.0203985320. The cubic root of 28291978 is about 304.7107461010.

The spelling of 28291978 in words is "twenty-eight million, two hundred ninety-one thousand, nine hundred seventy-eight".