28640661 has 32 divisors (see below), whose sum is σ = 45619200. Its totient is φ = 15637440.

The previous prime is 28640653. The next prime is 28640663. The reversal of 28640661 is 16604682.

It is a happy number.

It is not a de Polignac number, because 28640661 - 2³ = 28640653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28640663) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 79600 + ... + 79958.

It is an arithmetic number, because the mean of its divisors is an integer number (1425600).

Almost surely, 2^28640661 is an apocalyptic number.

28640661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

28640661 is a deficient number, since it is larger than the sum of its proper divisors (16978539).

28640661 is a wasteful number, since it uses less digits than its factorization.

28640661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 529.

The product of its (nonzero) digits is 13824, while the sum is 33.

The square root of 28640661 is about 5351.6970205721. The cubic root of 28640661 is about 305.9574356619.

The spelling of 28640661 in words is "twenty-eight million, six hundred forty thousand, six hundred sixty-one".