221278491 has 24 divisors (see below), whose sum is σ = 373062144. Its totient is φ = 123752880.

The previous prime is 221278487. The next prime is 221278513. The reversal of 221278491 is 194872122.

It is not a de Polignac number, because 221278491 - 2² = 221278487 is a prime.

It is a super-3 number, since 3×221278491³ (a number of 26 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (221278411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34405 + ... + 40326.

It is an arithmetic number, because the mean of its divisors is an integer number (15544256).

Almost surely, 2^221278491 is an apocalyptic number.

221278491 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

221278491 is a deficient number, since it is larger than the sum of its proper divisors (151783653).

221278491 is a wasteful number, since it uses less digits than its factorization.

221278491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74791 (or 74788 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 221278491 is about 14875.4324643017. The cubic root of 221278491 is about 604.8482109018.

The spelling of 221278491 in words is "two hundred twenty-one million, two hundred seventy-eight thousand, four hundred ninety-one".