661669 has 4 divisors (see below), whose sum is σ = 664000. Its totient is φ = 659340.

The previous prime is 661663. The next prime is 661673. The reversal of 661669 is 966166.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 661669 - 2⁷ = 661541 is a prime.

It is a super-2 number, since 2×661669² = 875611731122, which contains 22 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 (661663) 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, 669 + ... + 1330.

It is an arithmetic number, because the mean of its divisors is an integer number (166000).

2⁶⁶¹⁶⁶⁹ is an apocalyptic number.

It is an amenable number.

661669 is a deficient number, since it is larger than the sum of its proper divisors (2331).

661669 is a wasteful number, since it uses less digits than its factorization.

661669 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2330.

The product of its digits is 11664, while the sum is 34.

The square root of 661669 is about 813.4303903838. The cubic root of 661669 is about 87.1392055137.

The spelling of 661669 in words is "six hundred sixty-one thousand, six hundred sixty-nine".