661801 has 4 divisors (see below), whose sum is σ = 756352. Its totient is φ = 567252.

The previous prime is 661777. The next prime is 661823. The reversal of 661801 is 108166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 108166 = 2 ⋅54083.

It is not a de Polignac number, because 661801 - 2⁵ = 661769 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661201) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47265 + ... + 47278.

It is an arithmetic number, because the mean of its divisors is an integer number (189088).

2⁶⁶¹⁸⁰¹ is an apocalyptic number.

It is an amenable number.

661801 is a deficient number, since it is larger than the sum of its proper divisors (94551).

661801 is an equidigital number, since it uses as much as digits as its factorization.

661801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94550.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 661801 is about 813.5115241962. The cubic root of 661801 is about 87.1449997554.

Adding to 661801 its reverse (108166), we get a palindrome (769967).

The spelling of 661801 in words is "six hundred sixty-one thousand, eight hundred one".