20499581 has 6 divisors (see below), whose sum is σ = 20667582. Its totient is φ = 20332920.

The previous prime is 20499571. The next prime is 20499659. The reversal of 20499581 is 18599402.

It can be written as a sum of positive squares in only one way, i.e., 18567481 + 1932100 = 4309^2 + 1390^2 .

It is not a de Polignac number, because 20499581 - 2¹⁰ = 20498557 is a prime.

It is a super-2 number, since 2×20499581² = 840465642351122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20499511) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 18791 + ... + 19851.

It is an arithmetic number, because the mean of its divisors is an integer number (3444597).

Almost surely, 2^20499581 is an apocalyptic number.

It is an amenable number.

20499581 is a deficient number, since it is larger than the sum of its proper divisors (168001).

20499581 is an equidigital number, since it uses as much as digits as its factorization.

20499581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1339 (or 1200 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 38.

The square root of 20499581 is about 4527.6462980228. The cubic root of 20499581 is about 273.6833191078.

The spelling of 20499581 in words is "twenty million, four hundred ninety-nine thousand, five hundred eighty-one".