28661981 has 2 divisors, whose sum is σ = 28661982. Its totient is φ = 28661980.

The previous prime is 28661959. The next prime is 28661999. The reversal of 28661981 is 18916682.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 27730756 + 931225 = 5266^2 + 965^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28661981 is a prime.

It is a super-2 number, since 2×28661981² = 1643018309688722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28664981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14330990 + 14330991.

It is an arithmetic number, because the mean of its divisors is an integer number (14330991).

Almost surely, 2^28661981 is an apocalyptic number.

It is an amenable number.

28661981 is a deficient number, since it is larger than the sum of its proper divisors (1).

28661981 is an equidigital number, since it uses as much as digits as its factorization.

28661981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 41472, while the sum is 41.

The square root of 28661981 is about 5353.6885415571. The cubic root of 28661981 is about 306.0333346857.

The spelling of 28661981 in words is "twenty-eight million, six hundred sixty-one thousand, nine hundred eighty-one".