669499021 has 4 divisors (see below), whose sum is σ = 682131132. Its totient is φ = 656866912.

The previous prime is 669499013. The next prime is 669499027. The reversal of 669499021 is 120994966.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 357588100 + 311910921 = 18910^2 + 17661^2 .

It is a cyclic number.

It is not a de Polignac number, because 669499021 - 2³ = 669499013 is a prime.

It is a super-3 number, since 3×669499021³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (669499027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6315976 + ... + 6316081.

It is an arithmetic number, because the mean of its divisors is an integer number (170532783).

Almost surely, 2^669499021 is an apocalyptic number.

It is an amenable number.

669499021 is a deficient number, since it is larger than the sum of its proper divisors (12632111).

669499021 is a wasteful number, since it uses less digits than its factorization.

669499021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12632110.

The product of its (nonzero) digits is 209952, while the sum is 46.

The square root of 669499021 is about 25874.6791477692. The cubic root of 669499021 is about 874.8158615512.

The spelling of 669499021 in words is "six hundred sixty-nine million, four hundred ninety-nine thousand, twenty-one".