221078681 has 4 divisors (see below), whose sum is σ = 222692532. Its totient is φ = 219464832.

The previous prime is 221078677. The next prime is 221078731. The reversal of 221078681 is 186870122.

221078681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 137264656 + 83814025 = 11716^2 + 9155^2 .

It is a cyclic number.

It is not a de Polignac number, because 221078681 - 2² = 221078677 is a prime.

It is a super-2 number, since 2×221078681² = 97751566385399522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221078651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 806720 + ... + 806993.

It is an arithmetic number, because the mean of its divisors is an integer number (55673133).

Almost surely, 2^221078681 is an apocalyptic number.

It is an amenable number.

221078681 is a deficient number, since it is larger than the sum of its proper divisors (1613851).

221078681 is a wasteful number, since it uses less digits than its factorization.

221078681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1613850.

The product of its (nonzero) digits is 10752, while the sum is 35.

The square root of 221078681 is about 14868.7148402274. The cubic root of 221078681 is about 604.6661008450. Note that the first 3 decimals are identical.

The spelling of 221078681 in words is "two hundred twenty-one million, seventy-eight thousand, six hundred eighty-one".