221987538 has 24 divisors (see below), whose sum is σ = 486380700. Its totient is φ = 73163904.

The previous prime is 221987537. The next prime is 221987561. The reversal of 221987538 is 835789122.

It is a happy number.

221987538 is a `hidden beast` number, since 2 + 21 + 98 + 7 + 538 = 666.

221987538 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 220611609 + 1375929 = 14853^2 + 1173^2 .

It is a junction number, because it is equal to n+sod(n) for n = 221987493 and 221987502.

It is not an unprimeable number, because it can be changed into a prime (221987537) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 67683 + ... + 70886.

Almost surely, 2^221987538 is an apocalyptic number.

221987538 is an abundant number, since it is smaller than the sum of its proper divisors (264393162).

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

221987538 is a wasteful number, since it uses less digits than its factorization.

221987538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138666 (or 138663 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The square root of 221987538 is about 14899.2462225443. The cubic root of 221987538 is about 605.4935644061.

The spelling of 221987538 in words is "two hundred twenty-one million, nine hundred eighty-seven thousand, five hundred thirty-eight".