28451981 has 2 divisors, whose sum is σ = 28451982. Its totient is φ = 28451980.

The previous prime is 28451963. The next prime is 28451993. The reversal of 28451981 is 18915482.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19802500 + 8649481 = 4450^2 + 2941^2 .

It is a cyclic number.

It is not a de Polignac number, because 28451981 - 2¹⁰ = 28450957 is a prime.

It is a super-2 number, since 2×28451981² = 1619030445648722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28451881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14225990 + 14225991.

It is an arithmetic number, because the mean of its divisors is an integer number (14225991).

Almost surely, 2^28451981 is an apocalyptic number.

It is an amenable number.

28451981 is a deficient number, since it is larger than the sum of its proper divisors (1).

28451981 is an equidigital number, since it uses as much as digits as its factorization.

28451981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23040, while the sum is 38.

The square root of 28451981 is about 5334.0398386214. The cubic root of 28451981 is about 305.2840889746.

The spelling of 28451981 in words is "twenty-eight million, four hundred fifty-one thousand, nine hundred eighty-one".