6399827821 has 2 divisors, whose sum is σ = 6399827822. Its totient is φ = 6399827820.

The previous prime is 6399827743. The next prime is 6399827831. The reversal of 6399827821 is 1287289936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4731513796 + 1668314025 = 68786^2 + 40845^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6399827821 is a prime.

It is a super-2 number, since 2×6399827821² = 81915592276891216082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6399827831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3199913910 + 3199913911.

It is an arithmetic number, because the mean of its divisors is an integer number (3199913911).

Almost surely, 2^6399827821 is an apocalyptic number.

It is an amenable number.

6399827821 is a deficient number, since it is larger than the sum of its proper divisors (1).

6399827821 is an equidigital number, since it uses as much as digits as its factorization.

6399827821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2612736, while the sum is 55.

The square root of 6399827821 is about 79998.9238740122. The cubic root of 6399827821 is about 1856.6188836266.

It can be divided in two parts, 63998 and 27821, that added together give a palindrome (91819).

The spelling of 6399827821 in words is "six billion, three hundred ninety-nine million, eight hundred twenty-seven thousand, eight hundred twenty-one".