28637981 has 2 divisors, whose sum is σ = 28637982. Its totient is φ = 28637980.

The previous prime is 28637977. The next prime is 28638007. The reversal of 28637981 is 18973682.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27394756 + 1243225 = 5234^2 + 1115^2 .

It is a cyclic number.

It is not a de Polignac number, because 28637981 - 2² = 28637977 is a prime.

It is a super-2 number, since 2×28637981² = 1640267911512722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28637941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14318990 + 14318991.

It is an arithmetic number, because the mean of its divisors is an integer number (14318991).

Almost surely, 2^28637981 is an apocalyptic number.

It is an amenable number.

28637981 is a deficient number, since it is larger than the sum of its proper divisors (1).

28637981 is an equidigital number, since it uses as much as digits as its factorization.

28637981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 145152, while the sum is 44.

The square root of 28637981 is about 5351.4466268477. The cubic root of 28637981 is about 305.9478922194.

The spelling of 28637981 in words is "twenty-eight million, six hundred thirty-seven thousand, nine hundred eighty-one".