221720387 has 8 divisors (see below), whose sum is σ = 253730400. Its totient is φ = 189794304.

The previous prime is 221720381. The next prime is 221720393. The reversal of 221720387 is 783027122.

It is an interprime number because it is at equal distance from previous prime (221720381) and next prime (221720393).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 221720387 - 2⁸ = 221720131 is a prime.

It is a super-2 number, since 2×221720387² = 98319860022859538, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (221720381) 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, 15212 + ... + 25977.

It is an arithmetic number, because the mean of its divisors is an integer number (31716300).

Almost surely, 2^221720387 is an apocalyptic number.

221720387 is a deficient number, since it is larger than the sum of its proper divisors (32010013).

221720387 is an equidigital number, since it uses as much as digits as its factorization.

221720387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41965.

The product of its (nonzero) digits is 9408, while the sum is 32.

The square root of 221720387 is about 14890.2782714092. The cubic root of 221720387 is about 605.2505730721.

The spelling of 221720387 in words is "two hundred twenty-one million, seven hundred twenty thousand, three hundred eighty-seven".