20994581 has 4 divisors (see below), whose sum is σ = 21282252. Its totient is φ = 20706912.

The previous prime is 20994569. The next prime is 20994647. The reversal of 20994581 is 18549902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8213956 + 12780625 = 2866^2 + 3575^2 .

It is a cyclic number.

It is not a de Polignac number, because 20994581 - 2¹⁴ = 20978197 is a prime.

It is a super-2 number, since 2×20994581² = 881544862731122, 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 (20934581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143726 + ... + 143871.

It is an arithmetic number, because the mean of its divisors is an integer number (5320563).

Almost surely, 2^20994581 is an apocalyptic number.

It is an amenable number.

20994581 is a deficient number, since it is larger than the sum of its proper divisors (287671).

20994581 is an equidigital number, since it uses as much as digits as its factorization.

20994581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287670.

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

The square root of 20994581 is about 4581.9843954339. The cubic root of 20994581 is about 275.8686844694.

The spelling of 20994581 in words is "twenty million, nine hundred ninety-four thousand, five hundred eighty-one".