669921881 has 2 divisors, whose sum is σ = 669921882. Its totient is φ = 669921880.

The previous prime is 669921871. The next prime is 669921899. The reversal of 669921881 is 188129966.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 640545481 + 29376400 = 25309^2 + 5420^2 .

It is a cyclic number.

It is not a de Polignac number, because 669921881 - 2¹⁰ = 669920857 is a prime.

It is a super-2 number, since 2×669921881² = 897590653285156322, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (669921841) 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 as a sum of consecutive naturals, namely, 334960940 + 334960941.

It is an arithmetic number, because the mean of its divisors is an integer number (334960941).

Almost surely, 2^669921881 is an apocalyptic number.

It is an amenable number.

669921881 is a deficient number, since it is larger than the sum of its proper divisors (1).

669921881 is an equidigital number, since it uses as much as digits as its factorization.

669921881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 373248, while the sum is 50.

The square root of 669921881 is about 25882.8491669677. The cubic root of 669921881 is about 875.0000026122. Note that the first 5 decimals are identical.

The spelling of 669921881 in words is "six hundred sixty-nine million, nine hundred twenty-one thousand, eight hundred eighty-one".