261561503 has 4 divisors (see below), whose sum is σ = 298927440. Its totient is φ = 224195568.

The previous prime is 261561499. The next prime is 261561551. The reversal of 261561503 is 305165162.

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 261561503 - 2² = 261561499 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261561803) 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, 18682958 + ... + 18682971.

It is an arithmetic number, because the mean of its divisors is an integer number (74731860).

Almost surely, 2^261561503 is an apocalyptic number.

261561503 is a deficient number, since it is larger than the sum of its proper divisors (37365937).

261561503 is an equidigital number, since it uses as much as digits as its factorization.

261561503 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37365936.

The product of its (nonzero) digits is 5400, while the sum is 29.

The square root of 261561503 is about 16172.8631664279. The cubic root of 261561503 is about 639.5256111823.

The spelling of 261561503 in words is "two hundred sixty-one million, five hundred sixty-one thousand, five hundred three".