261404981 has 2 divisors, whose sum is σ = 261404982. Its totient is φ = 261404980.

The previous prime is 261404951. The next prime is 261404993. The reversal of 261404981 is 189404162.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 251222500 + 10182481 = 15850^2 + 3191^2 .

It is a cyclic number.

It is not a de Polignac number, because 261404981 - 2¹⁴ = 261388597 is a prime.

It is a super-2 number, since 2×261404981² = 136665128183220722, which contains 22 as substring.

It is equal to p_14268464 and since 261404981 and 14268464 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261404921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130702490 + 130702491.

It is an arithmetic number, because the mean of its divisors is an integer number (130702491).

Almost surely, 2^261404981 is an apocalyptic number.

It is an amenable number.

261404981 is a deficient number, since it is larger than the sum of its proper divisors (1).

261404981 is an equidigital number, since it uses as much as digits as its factorization.

261404981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 13824, while the sum is 35.

The square root of 261404981 is about 16168.0234104234. The cubic root of 261404981 is about 639.3980187547.

The spelling of 261404981 in words is "two hundred sixty-one million, four hundred four thousand, nine hundred eighty-one".