28639640 has 16 divisors (see below), whose sum is σ = 64439280. Its totient is φ = 11455840.

The previous prime is 28639627. The next prime is 28639649. The reversal of 28639640 is 4693682.

It is a junction number, because it is equal to n+sod(n) for n = 28639594 and 28639603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28639649) 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, 357956 + ... + 358035.

It is an arithmetic number, because the mean of its divisors is an integer number (4027455).

Almost surely, 2^28639640 is an apocalyptic number.

28639640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28639640 is an abundant number, since it is smaller than the sum of its proper divisors (35799640).

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

28639640 is a wasteful number, since it uses less digits than its factorization.

28639640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 716002 (or 715998 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 38.

The square root of 28639640 is about 5351.6016294190. The cubic root of 28639640 is about 305.9537999654.

The spelling of 28639640 in words is "twenty-eight million, six hundred thirty-nine thousand, six hundred forty".