261904981 has 8 divisors (see below), whose sum is σ = 289675064. Its totient is φ = 235224000.

The previous prime is 261904961. The next prime is 261904997. The reversal of 261904981 is 189409162.

It can be written as a sum of positive squares in 4 ways, for example, as 69639025 + 192265956 = 8345^2 + 13866^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261904981 - 2⁹ = 261904469 is a prime.

It is a super-2 number, since 2×261904981² = 137188438145220722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261904901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 271770 + ... + 272731.

It is an arithmetic number, because the mean of its divisors is an integer number (36209383).

Almost surely, 2^261904981 is an apocalyptic number.

It is an amenable number.

261904981 is a deficient number, since it is larger than the sum of its proper divisors (27770083).

261904981 is a wasteful number, since it uses less digits than its factorization.

261904981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 544551.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 261904981 is about 16183.4786433572. The cubic root of 261904981 is about 639.8054266915.

The spelling of 261904981 in words is "two hundred sixty-one million, nine hundred four thousand, nine hundred eighty-one".