261958221 has 12 divisors (see below), whose sum is σ = 432439072. Its totient is φ = 149690376.

The previous prime is 261958199. The next prime is 261958243. The reversal of 261958221 is 122859162.

It is an interprime number because it is at equal distance from previous prime (261958199) and next prime (261958243).

It is not a de Polignac number, because 261958221 - 2¹⁰ = 261957197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261958271) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2078971 + ... + 2079096.

Almost surely, 2^261958221 is an apocalyptic number.

261958221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

261958221 is a deficient number, since it is larger than the sum of its proper divisors (170480851).

261958221 is a wasteful number, since it uses less digits than its factorization.

261958221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4158080 (or 4158077 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 261958221 is about 16185.1234471659. The cubic root of 261958221 is about 639.8487769337.

The spelling of 261958221 in words is "two hundred sixty-one million, nine hundred fifty-eight thousand, two hundred twenty-one".