28661821 has 4 divisors (see below), whose sum is σ = 28690144. Its totient is φ = 28633500.

The previous prime is 28661819. The next prime is 28661837. The reversal of 28661821 is 12816682.

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 28661821 - 2¹ = 28661819 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 (28661891) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12585 + ... + 14686.

It is an arithmetic number, because the mean of its divisors is an integer number (7172536).

Almost surely, 2^28661821 is an apocalyptic number.

It is an amenable number.

28661821 is a deficient number, since it is larger than the sum of its proper divisors (28323).

28661821 is a wasteful number, since it uses less digits than its factorization.

28661821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28322.

The product of its digits is 9216, while the sum is 34.

The square root of 28661821 is about 5353.6735985676. The cubic root of 28661821 is about 306.0327652272.

The spelling of 28661821 in words is "twenty-eight million, six hundred sixty-one thousand, eight hundred twenty-one".