661764 has 12 divisors (see below), whose sum is σ = 1544144. Its totient is φ = 220584.

The previous prime is 661741. The next prime is 661769. The reversal of 661764 is 467166.

661764 is nontrivially palindromic in base 11.

It is a tau number, because it is divible by the number of its divisors (12).

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

661764 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27562 + ... + 27585.

2⁶⁶¹⁷⁶⁴ is an apocalyptic number.

It is an amenable number.

661764 is an abundant number, since it is smaller than the sum of its proper divisors (882380).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661764 is a wasteful number, since it uses less digits than its factorization.

661764 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55154 (or 55152 counting only the distinct ones).

The product of its digits is 6048, while the sum is 30.

The square root of 661764 is about 813.4887829589. The cubic root of 661764 is about 87.1433756896.

It can be divided in two parts, 66 and 1764, that added together give a triangular number (1830 = T₆₀).

The spelling of 661764 in words is "six hundred sixty-one thousand, seven hundred sixty-four".