261205513621 has 8 divisors (see below), whose sum is σ = 297845201304. Its totient is φ = 226929676800.

The previous prime is 261205513619. The next prime is 261205513627. The reversal of 261205513621 is 126315502162.

It can be written as a sum of positive squares in 4 ways, for example, as 18929907396 + 242275606225 = 137586^2 + 492215^2 .

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 261205513621 - 2¹ = 261205513619 is a prime.

It is a super-3 number, since 3×261205513621³ (a number of 35 digits) contains 333 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 (261205513627) 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, 590962480 + ... + 590962921.

It is an arithmetic number, because the mean of its divisors is an integer number (37230650163).

Almost surely, 2^261205513621 is an apocalyptic number.

It is an amenable number.

261205513621 is a deficient number, since it is larger than the sum of its proper divisors (36639687683).

261205513621 is a wasteful number, since it uses less digits than its factorization.

261205513621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1181925431.

The product of its (nonzero) digits is 21600, while the sum is 34.

The spelling of 261205513621 in words is "two hundred sixty-one billion, two hundred five million, five hundred thirteen thousand, six hundred twenty-one".