28655621 has 4 divisors (see below), whose sum is σ = 28670412. Its totient is φ = 28640832.

The previous prime is 28655617. The next prime is 28655633. The reversal of 28655621 is 12655682.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11730625 + 16924996 = 3425^2 + 4114^2 .

It is a cyclic number.

It is not a de Polignac number, because 28655621 - 2² = 28655617 is a prime.

It is a super-2 number, since 2×28655621² = 1642289229791282, 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 (28655611) 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, 3956 + ... + 8541.

It is an arithmetic number, because the mean of its divisors is an integer number (7167603).

Almost surely, 2^28655621 is an apocalyptic number.

It is an amenable number.

28655621 is a deficient number, since it is larger than the sum of its proper divisors (14791).

28655621 is a wasteful number, since it uses less digits than its factorization.

28655621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14790.

The product of its digits is 28800, while the sum is 35.

The square root of 28655621 is about 5353.0945255992. The cubic root of 28655621 is about 306.0106970786.

The spelling of 28655621 in words is "twenty-eight million, six hundred fifty-five thousand, six hundred twenty-one".