81601261 has 4 divisors (see below), whose sum is σ = 93258592. Its totient is φ = 69943932.

The previous prime is 81601253. The next prime is 81601277. The reversal of 81601261 is 16210618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81601261 - 2³ = 81601253 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81601231) 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, 5828655 + ... + 5828668.

It is an arithmetic number, because the mean of its divisors is an integer number (23314648).

Almost surely, 2^81601261 is an apocalyptic number.

It is an amenable number.

81601261 is a deficient number, since it is larger than the sum of its proper divisors (11657331).

81601261 is a wasteful number, since it uses less digits than its factorization.

81601261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11657330.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 81601261 is about 9033.3416297625. The cubic root of 81601261 is about 433.7428112986.

Adding to 81601261 its reverse (16210618), we get a palindrome (97811879).

The spelling of 81601261 in words is "eighty-one million, six hundred one thousand, two hundred sixty-one".