221601655 has 24 divisors (see below), whose sum is σ = 306195984. Its totient is φ = 152668800.

The previous prime is 221601649. The next prime is 221601689. The reversal of 221601655 is 556106122.

It is not a de Polignac number, because 221601655 - 2⁹ = 221601143 is a prime.

It is a super-4 number, since 4×221601655⁴ (a number of 34 digits) contains 4444 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14275 + ... + 25435.

It is an arithmetic number, because the mean of its divisors is an integer number (12758166).

Almost surely, 2^221601655 is an apocalyptic number.

221601655 is a deficient number, since it is larger than the sum of its proper divisors (84594329).

221601655 is a wasteful number, since it uses less digits than its factorization.

221601655 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11215 (or 11196 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 28.

The square root of 221601655 is about 14886.2908409046. The cubic root of 221601655 is about 605.1425158874.

Adding to 221601655 its reverse (556106122), we get a palindrome (777707777).

The spelling of 221601655 in words is "two hundred twenty-one million, six hundred one thousand, six hundred fifty-five".