1994165821 has 4 divisors (see below), whose sum is σ = 1994973372. Its totient is φ = 1993358272.

The previous prime is 1994165819. The next prime is 1994165837. The reversal of 1994165821 is 1285614991.

It is a happy number.

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 1535777721 + 458388100 = 39189^2 + 21410^2 .

It is a cyclic number.

It is not a de Polignac number, because 1994165821 - 2¹ = 1994165819 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1994165851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 400060 + ... + 405013.

It is an arithmetic number, because the mean of its divisors is an integer number (498743343).

Almost surely, 2^1994165821 is an apocalyptic number.

It is an amenable number.

1994165821 is a deficient number, since it is larger than the sum of its proper divisors (807551).

1994165821 is an equidigital number, since it uses as much as digits as its factorization.

1994165821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 807550.

The product of its digits is 155520, while the sum is 46.

The square root of 1994165821 is about 44656.0838072485. The cubic root of 1994165821 is about 1258.6947558958.

The spelling of 1994165821 in words is "one billion, nine hundred ninety-four million, one hundred sixty-five thousand, eight hundred twenty-one".