28756021 has 8 divisors (see below), whose sum is σ = 32970240. Its totient is φ = 24568368.

The previous prime is 28756009. The next prime is 28756033. The reversal of 28756021 is 12065782.

It is an interprime number because it is at equal distance from previous prime (28756009) and next prime (28756033).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 28756021 - 2¹⁹ = 28231733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28756001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4261 + ... + 8698.

It is an arithmetic number, because the mean of its divisors is an integer number (4121280).

Almost surely, 2^28756021 is an apocalyptic number.

It is an amenable number.

28756021 is a deficient number, since it is larger than the sum of its proper divisors (4214219).

28756021 is a wasteful number, since it uses less digits than its factorization.

28756021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13283.

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 28756021 is about 5362.4640791338. The cubic root of 28756021 is about 306.3676679032.

The spelling of 28756021 in words is "twenty-eight million, seven hundred fifty-six thousand, twenty-one".