28970821 has 4 divisors (see below), whose sum is σ = 31604544. Its totient is φ = 26337100.

The previous prime is 28970803. The next prime is 28970881. The reversal of 28970821 is 12807982.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 28970821 - 2⁵ = 28970789 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 (28970881) 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 3 ways as a sum of consecutive naturals, for example, 1316845 + ... + 1316866.

It is an arithmetic number, because the mean of its divisors is an integer number (7901136).

Almost surely, 2^28970821 is an apocalyptic number.

It is an amenable number.

28970821 is a deficient number, since it is larger than the sum of its proper divisors (2633723).

28970821 is a wasteful number, since it uses less digits than its factorization.

28970821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2633722.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 28970821 is about 5382.4549231740. The cubic root of 28970821 is about 307.1286053085.

It can be divided in two parts, 28970 and 821, that added together give a cube (29791 = 31³).

The spelling of 28970821 in words is "twenty-eight million, nine hundred seventy thousand, eight hundred twenty-one".