28637640 has 48 divisors (see below), whose sum is σ = 93073500. Its totient is φ = 7636608.

The previous prime is 28637629. The next prime is 28637657. The reversal of 28637640 is 4673682.

28637640 is a `hidden beast` number, since 2 + 8 + 6 + 3 + 7 + 640 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 26071236 + 2566404 = 5106^2 + 1602^2 .

It is a super-2 number, since 2×28637640² = 1640228849539200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 28637595 and 28637604.

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, 39415 + ... + 40134.

Almost surely, 2^28637640 is an apocalyptic number.

28637640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28637640 is an abundant number, since it is smaller than the sum of its proper divisors (64435860).

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

28637640 is a wasteful number, since it uses less digits than its factorization.

28637640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79566 (or 79559 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 36.

The square root of 28637640 is about 5351.4147662090. The cubic root of 28637640 is about 305.9466778805.

The spelling of 28637640 in words is "twenty-eight million, six hundred thirty-seven thousand, six hundred forty".