20491685 has 4 divisors (see below), whose sum is σ = 24590028. Its totient is φ = 16393344.

The previous prime is 20491631. The next prime is 20491699. The reversal of 20491685 is 58619402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 58619402 = 2 ⋅29309701.

It can be written as a sum of positive squares in 2 ways, for example, as 2910436 + 17581249 = 1706^2 + 4193^2 .

It is a cyclic number.

It is not a de Polignac number, because 20491685 - 2¹² = 20487589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2049164 + ... + 2049173.

It is an arithmetic number, because the mean of its divisors is an integer number (6147507).

Almost surely, 2^20491685 is an apocalyptic number.

It is an amenable number.

20491685 is a deficient number, since it is larger than the sum of its proper divisors (4098343).

20491685 is an equidigital number, since it uses as much as digits as its factorization.

20491685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4098342.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 20491685 is about 4526.7742377989. The cubic root of 20491685 is about 273.6481756090.

The spelling of 20491685 in words is "twenty million, four hundred ninety-one thousand, six hundred eighty-five".