661869 has 12 divisors (see below), whose sum is σ = 1029756. Its totient is φ = 407232.

The previous prime is 661849. The next prime is 661873. The reversal of 661869 is 968166.

661869 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 81225 + 580644 = 285^2 + 762^2 .

It is not a de Polignac number, because 661869 - 2⁷ = 661741 is a prime.

It is a super-2 number, since 2×661869² = 876141146322, which contains 22 as substring.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661849) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2712 + ... + 2945.

It is an arithmetic number, because the mean of its divisors is an integer number (85813).

2⁶⁶¹⁸⁶⁹ is an apocalyptic number.

It is an amenable number.

661869 is a deficient number, since it is larger than the sum of its proper divisors (367887).

661869 is a wasteful number, since it uses less digits than its factorization.

661869 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5676 (or 5673 counting only the distinct ones).

The product of its digits is 15552, while the sum is 36.

The square root of 661869 is about 813.5533172448. The cubic root of 661869 is about 87.1479843671.

The spelling of 661869 in words is "six hundred sixty-one thousand, eight hundred sixty-nine".