661901 has 4 divisors (see below), whose sum is σ = 676032. Its totient is φ = 647772.

The previous prime is 661897. The next prime is 661909. The reversal of 661901 is 109166.

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: 109166 = 2 ⋅54583.

It is a cyclic number.

It is not a de Polignac number, because 661901 - 2² = 661897 is a prime.

It is a super-2 number, since 2×661901² = 876225867602, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661909) 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, 6995 + ... + 7088.

It is an arithmetic number, because the mean of its divisors is an integer number (169008).

2⁶⁶¹⁹⁰¹ is an apocalyptic number.

It is an amenable number.

661901 is a deficient number, since it is larger than the sum of its proper divisors (14131).

661901 is a wasteful number, since it uses less digits than its factorization.

661901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14130.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 661901 is about 813.5729838189. The cubic root of 661901 is about 87.1493888195.

The spelling of 661901 in words is "six hundred sixty-one thousand, nine hundred one".