221681904 has 80 divisors (see below), whose sum is σ = 608987808. Its totient is φ = 69246976.

The previous prime is 221681903. The next prime is 221681909. The reversal of 221681904 is 409186122.

221681904 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×221681904² = 98285733122130432, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221681903) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 258244 + ... + 259100.

Almost surely, 2^221681904 is an apocalyptic number.

221681904 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221681904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (304493904).

221681904 is an abundant number, since it is smaller than the sum of its proper divisors (387305904).

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

221681904 is a wasteful number, since it uses less digits than its factorization.

221681904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1202 (or 1196 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 33.

The square root of 221681904 is about 14888.9859963666. The cubic root of 221681904 is about 605.2155541821.

The spelling of 221681904 in words is "two hundred twenty-one million, six hundred eighty-one thousand, nine hundred four".