261640621 has 8 divisors (see below), whose sum is σ = 300448800. Its totient is φ = 225336240.

The previous prime is 261640619. The next prime is 261640637. The reversal of 261640621 is 126046162.

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 261640621 - 2¹ = 261640619 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261640621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261640121) 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, 625726 + ... + 626143.

It is an arithmetic number, because the mean of its divisors is an integer number (37556100).

Almost surely, 2^261640621 is an apocalyptic number.

It is an amenable number.

261640621 is a deficient number, since it is larger than the sum of its proper divisors (38808179).

261640621 is a wasteful number, since it uses less digits than its factorization.

261640621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1251899.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 261640621 is about 16175.3089924119. The cubic root of 261640621 is about 639.5900866319.

Adding to 261640621 its reverse (126046162), we get a palindrome (387686783).

The spelling of 261640621 in words is "two hundred sixty-one million, six hundred forty thousand, six hundred twenty-one".