28312921 has 16 divisors (see below), whose sum is σ = 35018368. Its totient is φ = 22291200.

The previous prime is 28312901. The next prime is 28312943. The reversal of 28312921 is 12921382.

It is a 3-Lehmer number, since φ(28312921) divides (28312921-1)³.

It is a cyclic number.

It is not a de Polignac number, because 28312921 - 2⁹ = 28312409 is a prime.

It is a deceptive number, since it divides R_28312920.

It is a self number, because there is not a number n which added to its sum of digits gives 28312921.

It is not an unprimeable number, because it can be changed into a prime (28312901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21286 + ... + 22576.

It is an arithmetic number, because the mean of its divisors is an integer number (2188648).

It is a Poulet number, since it divides 2^28312920-1.

Almost surely, 2^28312921 is an apocalyptic number.

It is an amenable number.

28312921 is a deficient number, since it is larger than the sum of its proper divisors (6705447).

28312921 is a wasteful number, since it uses less digits than its factorization.

28312921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1552.

The product of its digits is 1728, while the sum is 28.

The square root of 28312921 is about 5320.9887239121. The cubic root of 28312921 is about 304.7859144422.

The spelling of 28312921 in words is "twenty-eight million, three hundred twelve thousand, nine hundred twenty-one".