221978920 has 32 divisors (see below), whose sum is σ = 511638120. Its totient is φ = 86625280.

The previous prime is 221978917. The next prime is 221978921. The reversal of 221978920 is 29879122.

It can be written as a sum of positive squares in 4 ways, for example, as 141086884 + 80892036 = 11878^2 + 8994^2 .

It is a Harshad number since it is a multiple of its sum of digits (40).

It is not an unprimeable number, because it can be changed into a prime (221978921) 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, 66037 + ... + 69316.

Almost surely, 2^221978920 is an apocalyptic number.

221978920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221978920 is an abundant number, since it is smaller than the sum of its proper divisors (289659200).

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

221978920 is a wasteful number, since it uses less digits than its factorization.

221978920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135405 (or 135401 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 221978920 is about 14898.9570104756. The cubic root of 221978920 is about 605.4857288145.

The spelling of 221978920 in words is "two hundred twenty-one million, nine hundred seventy-eight thousand, nine hundred twenty".