20181649 has 4 divisors (see below), whose sum is σ = 21059136. Its totient is φ = 19304164.

The previous prime is 20181643. The next prime is 20181671. The reversal of 20181649 is 94618102.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20181649 - 2⁷ = 20181521 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20181649.

It is not an unprimeable number, because it can be changed into a prime (20181643) by changing a digit.

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, 438709 + ... + 438754.

It is an arithmetic number, because the mean of its divisors is an integer number (5264784).

Almost surely, 2^20181649 is an apocalyptic number.

It is an amenable number.

20181649 is a deficient number, since it is larger than the sum of its proper divisors (877487).

20181649 is an equidigital number, since it uses as much as digits as its factorization.

20181649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 877486.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 20181649 is about 4492.3990250199. The cubic root of 20181649 is about 272.2610716054.

The spelling of 20181649 in words is "twenty million, one hundred eighty-one thousand, six hundred forty-nine".