221764681 has 4 divisors (see below), whose sum is σ = 221797764. Its totient is φ = 221731600.

The previous prime is 221764663. The next prime is 221764687. The reversal of 221764681 is 186467122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 186467122 = 2 ⋅93233561.

It can be written as a sum of positive squares in 2 ways, for example, as 165379600 + 56385081 = 12860^2 + 7509^2 .

It is a cyclic number.

It is not a de Polignac number, because 221764681 - 2⁷ = 221764553 is a prime.

It is a super-2 number, since 2×221764681² = 98359147478063522, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 221764681.

It is not an unprimeable number, because it can be changed into a prime (221764687) 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, 2530 + ... + 21211.

It is an arithmetic number, because the mean of its divisors is an integer number (55449441).

Almost surely, 2^221764681 is an apocalyptic number.

It is an amenable number.

221764681 is a deficient number, since it is larger than the sum of its proper divisors (33083).

221764681 is an equidigital number, since it uses as much as digits as its factorization.

221764681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33082.

The product of its digits is 32256, while the sum is 37.

The square root of 221764681 is about 14891.7655434136. The cubic root of 221764681 is about 605.2908748597.

The spelling of 221764681 in words is "two hundred twenty-one million, seven hundred sixty-four thousand, six hundred eighty-one".