20984581 has 2 divisors, whose sum is σ = 20984582. Its totient is φ = 20984580.

The previous prime is 20984503. The next prime is 20984599. The reversal of 20984581 is 18548902.

20984581 is nontrivially palindromic in base 15.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17355556 + 3629025 = 4166^2 + 1905^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20984581 is a prime.

It is a super-2 number, since 2×20984581² = 880705279491122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20984581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20984881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10492290 + 10492291.

It is an arithmetic number, because the mean of its divisors is an integer number (10492291).

Almost surely, 2^20984581 is an apocalyptic number.

It is an amenable number.

20984581 is a deficient number, since it is larger than the sum of its proper divisors (1).

20984581 is an equidigital number, since it uses as much as digits as its factorization.

20984581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23040, while the sum is 37.

The square root of 20984581 is about 4580.8930352061. The cubic root of 20984581 is about 275.8248775308.

The spelling of 20984581 in words is "twenty million, nine hundred eighty-four thousand, five hundred eighty-one".