669521947 has 4 divisors (see below), whose sum is σ = 673786576. Its totient is φ = 665257320.

The previous prime is 669521899. The next prime is 669521959. The reversal of 669521947 is 749125966.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 749125966 = 2 ⋅374562983.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-669521947 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 669521947.

It is not an unprimeable number, because it can be changed into a prime (669521987) 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, 2132079 + ... + 2132392.

It is an arithmetic number, because the mean of its divisors is an integer number (168446644).

Almost surely, 2^669521947 is an apocalyptic number.

669521947 is a deficient number, since it is larger than the sum of its proper divisors (4264629).

669521947 is a wasteful number, since it uses less digits than its factorization.

669521947 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4264628.

The product of its digits is 816480, while the sum is 49.

The square root of 669521947 is about 25875.1221639628. The cubic root of 669521947 is about 874.8258470274.

The spelling of 669521947 in words is "six hundred sixty-nine million, five hundred twenty-one thousand, nine hundred forty-seven".