661620 has 24 divisors (see below), whose sum is σ = 1852704. Its totient is φ = 176416.

The previous prime is 661613. The next prime is 661621. The reversal of 661620 is 26166.

It is a hoax number, since the sum of its digits (21) coincides with the sum of the digits of its distinct prime factors.

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 661620.

It is not an unprimeable number, because it can be changed into a prime (661621) by changing a digit.

661620 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 7 ways as a sum of consecutive naturals, for example, 5454 + ... + 5573.

It is an arithmetic number, because the mean of its divisors is an integer number (77196).

2⁶⁶¹⁶²⁰ is an apocalyptic number.

661620 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661620 is an abundant number, since it is smaller than the sum of its proper divisors (1191084).

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

661620 is a wasteful number, since it uses less digits than its factorization.

661620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11039 (or 11037 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 661620 is about 813.4002704696. The cubic root of 661620 is about 87.1370544248.

Adding to 661620 its reverse (26166), we get a palindrome (687786).

The spelling of 661620 in words is "six hundred sixty-one thousand, six hundred twenty".