221777921 has 8 divisors (see below), whose sum is σ = 224278824. Its totient is φ = 219283200.

The previous prime is 221777887. The next prime is 221777951. The reversal of 221777921 is 129777122.

It can be written as a sum of positive squares in 4 ways, for example, as 155127025 + 66650896 = 12455^2 + 8164^2 .

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 221777921 - 2¹⁰ = 221776897 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221777951) 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, 130151 + ... + 131843.

It is an arithmetic number, because the mean of its divisors is an integer number (28034853).

Almost surely, 2^221777921 is an apocalyptic number.

It is an amenable number.

221777921 is a deficient number, since it is larger than the sum of its proper divisors (2500903).

221777921 is a wasteful number, since it uses less digits than its factorization.

221777921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3091.

The product of its digits is 24696, while the sum is 38.

The square root of 221777921 is about 14892.2100777554. The cubic root of 221777921 is about 605.3029204984.

The spelling of 221777921 in words is "two hundred twenty-one million, seven hundred seventy-seven thousand, nine hundred twenty-one".