1955816821 has 6 divisors (see below), whose sum is σ = 2275133910. Its totient is φ = 1676414376.

The previous prime is 1955816761. The next prime is 1955816843. The reversal of 1955816821 is 1286185591.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 1947898225 + 7918596 = 44135^2 + 2814^2 .

It is not a de Polignac number, because 1955816821 - 2⁹ = 1955816309 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1955816881) 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 in 5 ways as a sum of consecutive naturals, for example, 19957266 + ... + 19957363.

It is an arithmetic number, because the mean of its divisors is an integer number (379188985).

Almost surely, 2^1955816821 is an apocalyptic number.

It is an amenable number.

1955816821 is a deficient number, since it is larger than the sum of its proper divisors (319317089).

1955816821 is an equidigital number, since it uses as much as digits as its factorization.

1955816821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39914643 (or 39914636 counting only the distinct ones).

The product of its digits is 172800, while the sum is 46.

The square root of 1955816821 is about 44224.6178163249. The cubic root of 1955816821 is about 1250.5739915333.

The spelling of 1955816821 in words is "one billion, nine hundred fifty-five million, eight hundred sixteen thousand, eight hundred twenty-one".