669872821 has 2 divisors, whose sum is σ = 669872822. Its totient is φ = 669872820.

The previous prime is 669872741. The next prime is 669872851. The reversal of 669872821 is 128278966.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 592679025 + 77193796 = 24345^2 + 8786^2 .

It is a cyclic number.

It is not a de Polignac number, because 669872821 - 2¹⁵ = 669840053 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (669872851) 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 as a sum of consecutive naturals, namely, 334936410 + 334936411.

It is an arithmetic number, because the mean of its divisors is an integer number (334936411).

Almost surely, 2^669872821 is an apocalyptic number.

It is an amenable number.

669872821 is a deficient number, since it is larger than the sum of its proper divisors (1).

669872821 is an equidigital number, since it uses as much as digits as its factorization.

669872821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 580608, while the sum is 49.

The square root of 669872821 is about 25881.9014177861. The cubic root of 669872821 is about 874.9786426352.

The spelling of 669872821 in words is "six hundred sixty-nine million, eight hundred seventy-two thousand, eight hundred twenty-one".