661569 has 8 divisors (see below), whose sum is σ = 891072. Its totient is φ = 436560.

The previous prime is 661553. The next prime is 661603. The reversal of 661569 is 965166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661569 - 2⁴ = 661553 is a prime.

It is a super-2 number, since 2×661569² = 875347083522, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (661769) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 762 + ... + 1379.

It is an arithmetic number, because the mean of its divisors is an integer number (111384).

2⁶⁶¹⁵⁶⁹ is an apocalyptic number.

It is an amenable number.

661569 is a deficient number, since it is larger than the sum of its proper divisors (229503).

661569 is a wasteful number, since it uses less digits than its factorization.

661569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2247.

The product of its digits is 9720, while the sum is 33.

The square root of 661569 is about 813.3689199865. The cubic root of 661569 is about 87.1348154236.

The spelling of 661569 in words is "six hundred sixty-one thousand, five hundred sixty-nine".