669521 has 4 divisors (see below), whose sum is σ = 671232. Its totient is φ = 667812.

The previous prime is 669481. The next prime is 669527. The reversal of 669521 is 125966.

669521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 125966 = 2 ⋅62983.

It is a cyclic number.

It is not a de Polignac number, because 669521 - 2¹⁸ = 407377 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 669521.

It is not an unprimeable number, because it can be changed into a prime (669527) 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, 56 + ... + 1158.

It is an arithmetic number, because the mean of its divisors is an integer number (167808).

2⁶⁶⁹⁵²¹ is an apocalyptic number.

It is an amenable number.

669521 is a deficient number, since it is larger than the sum of its proper divisors (1711).

669521 is a wasteful number, since it uses less digits than its factorization.

669521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1710.

The product of its digits is 3240, while the sum is 29.

The square root of 669521 is about 818.2426290533. The cubic root of 669521 is about 87.4825434564.

The spelling of 669521 in words is "six hundred sixty-nine thousand, five hundred twenty-one".