261311023 has 4 divisors (see below), whose sum is σ = 266870880. Its totient is φ = 255751168.

The previous prime is 261310993. The next prime is 261311077. The reversal of 261311023 is 320113162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 261311023 - 2¹³ = 261302831 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 (261311093) 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, 2779858 + ... + 2779951.

It is an arithmetic number, because the mean of its divisors is an integer number (66717720).

Almost surely, 2^261311023 is an apocalyptic number.

261311023 is a deficient number, since it is larger than the sum of its proper divisors (5559857).

261311023 is an equidigital number, since it uses as much as digits as its factorization.

261311023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5559856.

The product of its (nonzero) digits is 216, while the sum is 19.

The square root of 261311023 is about 16165.1174756016. The cubic root of 261311023 is about 639.3214023132.

Adding to 261311023 its reverse (320113162), we get a palindrome (581424185).

The spelling of 261311023 in words is "two hundred sixty-one million, three hundred eleven thousand, twenty-three".