261218081 has 2 divisors, whose sum is σ = 261218082. Its totient is φ = 261218080.

The previous prime is 261218053. The next prime is 261218117. The reversal of 261218081 is 180812162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 196560400 + 64657681 = 14020^2 + 8041^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261218081 is a prime.

It is a super-2 number, since 2×261218081² = 136469771682645122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (261218281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130609040 + 130609041.

It is an arithmetic number, because the mean of its divisors is an integer number (130609041).

Almost surely, 2^261218081 is an apocalyptic number.

It is an amenable number.

261218081 is a deficient number, since it is larger than the sum of its proper divisors (1).

261218081 is an equidigital number, since it uses as much as digits as its factorization.

261218081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1536, while the sum is 29.

The square root of 261218081 is about 16162.2424496108. The cubic root of 261218081 is about 639.2455962804.

The spelling of 261218081 in words is "two hundred sixty-one million, two hundred eighteen thousand, eighty-one".