661020 has 48 divisors (see below), whose sum is σ = 1935360. Its totient is φ = 168256.

The previous prime is 661019. The next prime is 661027. The reversal of 661020 is 20166.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1141 + ... + 1619.

It is an arithmetic number, because the mean of its divisors is an integer number (40320).

2⁶⁶¹⁰²⁰ is an apocalyptic number.

661020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (967680).

661020 is an abundant number, since it is smaller than the sum of its proper divisors (1274340).

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

661020 is a wasteful number, since it uses less digits than its factorization.

661020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 514 (or 512 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 15.

The square root of 661020 is about 813.0313647086. The cubic root of 661020 is about 87.1107059443.

Adding to 661020 its reverse (20166), we get a palindrome (681186).

The spelling of 661020 in words is "six hundred sixty-one thousand, twenty".