221508981 has 12 divisors (see below), whose sum is σ = 330279040. Its totient is φ = 142908840.

The previous prime is 221508977. The next prime is 221509009. The reversal of 221508981 is 189805122.

It is not a de Polignac number, because 221508981 - 2² = 221508977 is a prime.

It is a super-2 number, since 2×221508981² = 98132457327316722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221508941) 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, 396691 + ... + 397248.

Almost surely, 2^221508981 is an apocalyptic number.

It is an amenable number.

221508981 is a deficient number, since it is larger than the sum of its proper divisors (108770059).

221508981 is a wasteful number, since it uses less digits than its factorization.

221508981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 793976 (or 793973 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 36.

The square root of 221508981 is about 14883.1777856747. The cubic root of 221508981 is about 605.0581470875.

The spelling of 221508981 in words is "two hundred twenty-one million, five hundred eight thousand, nine hundred eighty-one".