661819 has 8 divisors (see below), whose sum is σ = 702848. Its totient is φ = 622080.

The previous prime is 661777. The next prime is 661823. The reversal of 661819 is 918166.

It is a happy number.

661819 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661819 is a prime.

It is a super-2 number, since 2×661819² = 876008777522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian 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 7 ways as a sum of consecutive naturals, for example, 859 + ... + 1435.

It is an arithmetic number, because the mean of its divisors is an integer number (87856).

2⁶⁶¹⁸¹⁹ is an apocalyptic number.

661819 is a deficient number, since it is larger than the sum of its proper divisors (41029).

661819 is a wasteful number, since it uses less digits than its factorization.

661819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645.

The product of its digits is 2592, while the sum is 31.

The square root of 661819 is about 813.5225872709. The cubic root of 661819 is about 87.1457898195.

The spelling of 661819 in words is "six hundred sixty-one thousand, eight hundred nineteen".