28784854921 has 3 divisors (see below), whose sum is σ = 28785024583. Its totient is φ = 28784685260.

The previous prime is 28784854909. The next prime is 28784855017. The reversal of 28784854921 is 12945848782.

The square root of 28784854921 is 169661.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 10844931321 + 17939923600 = 104139^2 + 133940^2 .

It is not a de Polignac number, because 28784854921 - 2⁹ = 28784854409 is a prime.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28784254921) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 84831 + ... + 254491.

Almost surely, 2^28784854921 is an apocalyptic number.

28784854921 is the 169661-st square number.

28784854921 is the 84831-st centered octagonal number.

It is an amenable number.

28784854921 is a deficient number, since it is larger than the sum of its proper divisors (169662).

28784854921 is an frugal number, since it uses more digits than its factorization.

28784854921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 339322 (or 169661 counting only the distinct ones).

The product of its digits is 10321920, while the sum is 58.

The spelling of 28784854921 in words is "twenty-eight billion, seven hundred eighty-four million, eight hundred fifty-four thousand, nine hundred twenty-one".