221721264 has 30 divisors (see below), whose sum is σ = 620511996. Its totient is φ = 73907040.

The previous prime is 221721257. The next prime is 221721277. The reversal of 221721264 is 462127122.

221721264 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 769722 + ... + 770009.

Almost surely, 2^221721264 is an apocalyptic number.

221721264 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

221721264 is an abundant number, since it is smaller than the sum of its proper divisors (398790732).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

221721264 is a wasteful number, since it uses less digits than its factorization.

221721264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1539745 (or 1539736 counting only the distinct ones).

The product of its digits is 2688, while the sum is 27.

The square root of 221721264 is about 14890.3077201245. The cubic root of 221721264 is about 605.2513710803.

Adding to 221721264 its reverse (462127122), we get a palindrome (683848386).

It can be divided in two parts, 22172 and 1264, that added together give a triangular number (23436 = T₂₁₆).

The spelling of 221721264 in words is "two hundred twenty-one million, seven hundred twenty-one thousand, two hundred sixty-four".