661261 has 8 divisors (see below), whose sum is σ = 693504. Its totient is φ = 629760.

The previous prime is 661259. The next prime is 661267. The reversal of 661261 is 162166.

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

It is a cyclic number.

It is not a de Polignac number, because 661261 - 2¹ = 661259 is a prime.

It is a super-2 number, since 2×661261² = 874532220242, 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 (661267) 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, 2445 + ... + 2701.

It is an arithmetic number, because the mean of its divisors is an integer number (86688).

2⁶⁶¹²⁶¹ is an apocalyptic number.

It is an amenable number.

661261 is a deficient number, since it is larger than the sum of its proper divisors (32243).

661261 is a wasteful number, since it uses less digits than its factorization.

661261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 371.

The product of its digits is 432, while the sum is 22.

The square root of 661261 is about 813.1795619665. The cubic root of 661261 is about 87.1212911658.

The spelling of 661261 in words is "six hundred sixty-one thousand, two hundred sixty-one".