28157978 has 4 divisors (see below), whose sum is σ = 42236970. Its totient is φ = 14078988.

The previous prime is 28157977. The next prime is 28157993. The reversal of 28157978 is 87975182.

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

It can be written as a sum of positive squares in only one way, i.e., 28015849 + 142129 = 5293^2 + 377^2 .

It is not an unprimeable number, because it can be changed into a prime (28157971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7039493 + ... + 7039496.

Almost surely, 2^28157978 is an apocalyptic number.

28157978 is a deficient number, since it is larger than the sum of its proper divisors (14078992).

28157978 is a wasteful number, since it uses less digits than its factorization.

28157978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14078991.

The product of its digits is 282240, while the sum is 47.

The square root of 28157978 is about 5306.4091436677. The cubic root of 28157978 is about 304.2289148970.

The spelling of 28157978 in words is "twenty-eight million, one hundred fifty-seven thousand, nine hundred seventy-eight".