661428 has 36 divisors (see below), whose sum is σ = 1761760. Its totient is φ = 208656.

The previous prime is 661421. The next prime is 661439. The reversal of 661428 is 824166.

661428 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 661428.

It is not an unprimeable number, because it can be changed into a prime (661421) 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, 201 + ... + 1167.

2⁶⁶¹⁴²⁸ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661428, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (880880).

661428 is an abundant number, since it is smaller than the sum of its proper divisors (1100332).

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

661428 is a wasteful number, since it uses less digits than its factorization.

661428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 996 (or 991 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 661428 is about 813.2822388323. The cubic root of 661428 is about 87.1286246448.

It can be divided in two parts, 661 and 428, that added together give a square (1089 = 33²).

The spelling of 661428 in words is "six hundred sixty-one thousand, four hundred twenty-eight".