669351821 has 2 divisors, whose sum is σ = 669351822. Its totient is φ = 669351820.

The previous prime is 669351791. The next prime is 669351877. The reversal of 669351821 is 128153966.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 648975625 + 20376196 = 25475^2 + 4514^2 .

It is a cyclic number.

It is not a de Polignac number, because 669351821 - 2¹⁴ = 669335437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (669353821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334675910 + 334675911.

It is an arithmetic number, because the mean of its divisors is an integer number (334675911).

Almost surely, 2^669351821 is an apocalyptic number.

It is an amenable number.

669351821 is a deficient number, since it is larger than the sum of its proper divisors (1).

669351821 is an equidigital number, since it uses as much as digits as its factorization.

669351821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 77760, while the sum is 41.

The square root of 669351821 is about 25871.8345116847. The cubic root of 669351821 is about 874.7517427950.

The spelling of 669351821 in words is "six hundred sixty-nine million, three hundred fifty-one thousand, eight hundred twenty-one".