669921871 has 2 divisors, whose sum is σ = 669921872. Its totient is φ = 669921870.

The previous prime is 669921869. The next prime is 669921881. The reversal of 669921871 is 178129966.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 669921871 - 2¹ = 669921869 is a prime.

Together with 669921869, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (669921841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334960935 + 334960936.

It is an arithmetic number, because the mean of its divisors is an integer number (334960936).

Almost surely, 2^669921871 is an apocalyptic number.

669921871 is a deficient number, since it is larger than the sum of its proper divisors (1).

669921871 is an equidigital number, since it uses as much as digits as its factorization.

669921871 is an evil number, because the sum of its binary digits is even.

The product of its digits is 326592, while the sum is 49.

The square root of 669921871 is about 25882.8489737896. The cubic root of 669921871 is about 874.9999982585. Note that the first 5 decimals are identical.

The spelling of 669921871 in words is "six hundred sixty-nine million, nine hundred twenty-one thousand, eight hundred seventy-one".