28505981 has 8 divisors (see below), whose sum is σ = 32813760. Its totient is φ = 24257088.

The previous prime is 28505969. The next prime is 28506011. The reversal of 28505981 is 18950582.

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

It is a cyclic number.

It is not a de Polignac number, because 28505981 - 2¹⁴ = 28489597 is a prime.

It is a super-2 number, since 2×28505981² = 1625181905544722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28505381) 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, 13676 + ... + 15621.

It is an arithmetic number, because the mean of its divisors is an integer number (4101720).

Almost surely, 2^28505981 is an apocalyptic number.

It is an amenable number.

28505981 is a deficient number, since it is larger than the sum of its proper divisors (4307779).

28505981 is a wasteful number, since it uses less digits than its factorization.

28505981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29443.

The product of its (nonzero) digits is 28800, while the sum is 38.

The square root of 28505981 is about 5339.0992686033. The cubic root of 28505981 is about 305.4771033312.

The spelling of 28505981 in words is "twenty-eight million, five hundred five thousand, nine hundred eighty-one".