261261578 has 4 divisors (see below), whose sum is σ = 391892370. Its totient is φ = 130630788.

The previous prime is 261261569. The next prime is 261261587. The reversal of 261261578 is 875162162.

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

It is an interprime number because it is at equal distance from previous prime (261261569) and next prime (261261587).

It can be written as a sum of positive squares in only one way, i.e., 176013289 + 85248289 = 13267^2 + 9233^2 .

It is a super-2 number, since 2×261261578² = 136515224278100168, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 65315393 + ... + 65315396.

Almost surely, 2^261261578 is an apocalyptic number.

261261578 is a deficient number, since it is larger than the sum of its proper divisors (130630792).

261261578 is a wasteful number, since it uses less digits than its factorization.

261261578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130630791.

The product of its digits is 40320, while the sum is 38.

The square root of 261261578 is about 16163.5880298899. The cubic root of 261261578 is about 639.2810758593.

The spelling of 261261578 in words is "two hundred sixty-one million, two hundred sixty-one thousand, five hundred seventy-eight".