261572551 has 4 divisors (see below), whose sum is σ = 261617992. Its totient is φ = 261527112.

The previous prime is 261572539. The next prime is 261572561. The reversal of 261572551 is 155275162.

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 261572551 - 2⁹ = 261572039 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 (261572501) 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, 12576 + ... + 26101.

It is an arithmetic number, because the mean of its divisors is an integer number (65404498).

Almost surely, 2^261572551 is an apocalyptic number.

261572551 is a deficient number, since it is larger than the sum of its proper divisors (45441).

261572551 is an equidigital number, since it uses as much as digits as its factorization.

261572551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45440.

The product of its digits is 21000, while the sum is 34.

The square root of 261572551 is about 16173.2047226269. The cubic root of 261572551 is about 639.5346152845.

The spelling of 261572551 in words is "two hundred sixty-one million, five hundred seventy-two thousand, five hundred fifty-one".