20181949 has 2 divisors, whose sum is σ = 20181950. Its totient is φ = 20181948.

The previous prime is 20181947. The next prime is 20181979. The reversal of 20181949 is 94918102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19404025 + 777924 = 4405^2 + 882^2 .

It is a cyclic number.

It is not a de Polignac number, because 20181949 - 2¹ = 20181947 is a prime.

It is a super-2 number, since 2×20181949² = 814622130877202, which contains 22 as substring.

Together with 20181947, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20181947) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10090974 + 10090975.

It is an arithmetic number, because the mean of its divisors is an integer number (10090975).

Almost surely, 2^20181949 is an apocalyptic number.

It is an amenable number.

20181949 is a deficient number, since it is larger than the sum of its proper divisors (1).

20181949 is an equidigital number, since it uses as much as digits as its factorization.

20181949 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 20181949 is about 4492.4324146280. The cubic root of 20181949 is about 272.2624206514.

The spelling of 20181949 in words is "twenty million, one hundred eighty-one thousand, nine hundred forty-nine".