261572581 has 4 divisors (see below), whose sum is σ = 262231852. Its totient is φ = 260913312.

The previous prime is 261572567. The next prime is 261572587. The reversal of 261572581 is 185275162.

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

It can be written as a sum of positive squares in 2 ways, for example, as 122544900 + 139027681 = 11070^2 + 11791^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261572581 is a prime.

It is a super-2 number, since 2×261572581² = 136840430262003122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261572581.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261572587) 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, 329040 + ... + 329833.

It is an arithmetic number, because the mean of its divisors is an integer number (65557963).

Almost surely, 2^261572581 is an apocalyptic number.

It is an amenable number.

261572581 is a deficient number, since it is larger than the sum of its proper divisors (659271).

261572581 is an equidigital number, since it uses as much as digits as its factorization.

261572581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 659270.

The product of its digits is 33600, while the sum is 37.

The square root of 261572581 is about 16173.2056500868. The cubic root of 261572581 is about 639.5346397341.

The spelling of 261572581 in words is "two hundred sixty-one million, five hundred seventy-two thousand, five hundred eighty-one".