261323501 has 4 divisors (see below), whose sum is σ = 263077500. Its totient is φ = 259569504.

The previous prime is 261323483. The next prime is 261323509. The reversal of 261323501 is 105323162.

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 155027401 + 106296100 = 12451^2 + 10310^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261323501 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 (261323509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 876776 + ... + 877073.

It is an arithmetic number, because the mean of its divisors is an integer number (65769375).

Almost surely, 2^261323501 is an apocalyptic number.

It is an amenable number.

261323501 is a deficient number, since it is larger than the sum of its proper divisors (1753999).

261323501 is a wasteful number, since it uses less digits than its factorization.

261323501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1753998.

The product of its (nonzero) digits is 1080, while the sum is 23.

The square root of 261323501 is about 16165.5034255046. The cubic root of 261323501 is about 639.3315783420.

Adding to 261323501 its reverse (105323162), we get a palindrome (366646663).

The spelling of 261323501 in words is "two hundred sixty-one million, three hundred twenty-three thousand, five hundred one".