261116621 has 4 divisors (see below), whose sum is σ = 265013952. Its totient is φ = 257219292.

The previous prime is 261116593. The next prime is 261116633. The reversal of 261116621 is 126611162.

261116621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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: 126611162 = 2 ⋅63305581.

It is a cyclic number.

It is not a de Polignac number, because 261116621 - 2¹⁴ = 261100237 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261116321) 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, 1948565 + ... + 1948698.

It is an arithmetic number, because the mean of its divisors is an integer number (66253488).

Almost surely, 2^261116621 is an apocalyptic number.

It is an amenable number.

261116621 is a deficient number, since it is larger than the sum of its proper divisors (3897331).

261116621 is an equidigital number, since it uses as much as digits as its factorization.

261116621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3897330.

The product of its digits is 864, while the sum is 26.

The square root of 261116621 is about 16159.1033476490. The cubic root of 261116621 is about 639.1628222028.

Adding to 261116621 its reverse (126611162), we get a palindrome (387727783).

It can be divided in two parts, 261116 and 621, that multiplied together give a triangular number (162153036 = T₁₈₀₀₈).

The spelling of 261116621 in words is "two hundred sixty-one million, one hundred sixteen thousand, six hundred twenty-one".