28861221 has 8 divisors (see below), whose sum is σ = 39521824. Its totient is φ = 18720720.

The previous prime is 28861219. The next prime is 28861237. The reversal of 28861221 is 12216882.

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

It is not a de Polignac number, because 28861221 - 2¹ = 28861219 is a prime.

It is a super-2 number, since 2×28861221² = 1665940155221682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28861201) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 129895 + ... + 130116.

It is an arithmetic number, because the mean of its divisors is an integer number (4940228).

Almost surely, 2^28861221 is an apocalyptic number.

It is an amenable number.

28861221 is a deficient number, since it is larger than the sum of its proper divisors (10660603).

28861221 is a wasteful number, since it uses less digits than its factorization.

28861221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260051.

The product of its digits is 3072, while the sum is 30.

The square root of 28861221 is about 5372.2640478666. The cubic root of 28861221 is about 306.7408147475.

The spelling of 28861221 in words is "twenty-eight million, eight hundred sixty-one thousand, two hundred twenty-one".