261493991 has 8 divisors (see below), whose sum is σ = 285584400.
Its totient is φ = 237456640.
The previous prime is 261493951. The next prime is 261493993. The reversal of 261493991 is 199394162.
It is a happy number.
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 261493991 - 214 = 261477607 is a prime.
It is a Duffinian number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (261493993) 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, 2576 + ... + 23013.
It is an arithmetic number, because the mean of its divisors is an integer number (35698050).
Almost surely, 2261493991 is an apocalyptic number.
261493991 is a deficient number, since it is larger than the sum of its proper divisors (24090409).
261493991 is a wasteful number, since it uses less digits than its factorization.
261493991 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 26529.
The product of its digits is 104976, while the sum is 44.
The square root of 261493991 is about 16170.7758317280.
The cubic root of 261493991 is about 639.4705835020.
The spelling of 261493991 in words is "two hundred sixty-one million, four hundred ninety-three thousand, nine hundred ninety-one".