28666639 has 2 divisors, whose sum is σ = 28666640. Its totient is φ = 28666638.

The previous prime is 28666621. The next prime is 28666643. The reversal of 28666639 is 93666682.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 28666639 - 2¹⁷ = 28535567 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28666609) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14333319 + 14333320.

It is an arithmetic number, because the mean of its divisors is an integer number (14333320).

Almost surely, 2^28666639 is an apocalyptic number.

28666639 is a deficient number, since it is larger than the sum of its proper divisors (1).

28666639 is an equidigital number, since it uses as much as digits as its factorization.

28666639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 559872, while the sum is 46.

The square root of 28666639 is about 5354.1235510586. The cubic root of 28666639 is about 306.0499121169.

The spelling of 28666639 in words is "twenty-eight million, six hundred sixty-six thousand, six hundred thirty-nine".