221380661 has 4 divisors (see below), whose sum is σ = 222660492. Its totient is φ = 220100832.

The previous prime is 221380631. The next prime is 221380741. The reversal of 221380661 is 166083122.

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 107019025 + 114361636 = 10345^2 + 10694^2 .

It is a cyclic number.

It is not a de Polignac number, because 221380661 - 2⁶ = 221380597 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 (221380631) 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, 639656 + ... + 640001.

It is an arithmetic number, because the mean of its divisors is an integer number (55665123).

Almost surely, 2^221380661 is an apocalyptic number.

It is an amenable number.

221380661 is a deficient number, since it is larger than the sum of its proper divisors (1279831).

221380661 is a wasteful number, since it uses less digits than its factorization.

221380661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1279830.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 221380661 is about 14878.8662538515. The cubic root of 221380661 is about 604.9412879300.

The spelling of 221380661 in words is "two hundred twenty-one million, three hundred eighty thousand, six hundred sixty-one".