21989236 has 12 divisors (see below), whose sum is σ = 38579940. Its totient is φ = 10966400.

The previous prime is 21989207. The next prime is 21989237. The reversal of 21989236 is 63298912.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20757136 + 1232100 = 4556^2 + 1110^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21989237) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5251 + ... + 8458.

It is an arithmetic number, because the mean of its divisors is an integer number (3214995).

Almost surely, 2^21989236 is an apocalyptic number.

It is an amenable number.

21989236 is a deficient number, since it is larger than the sum of its proper divisors (16590704).

21989236 is a wasteful number, since it uses less digits than its factorization.

21989236 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14114 (or 14112 counting only the distinct ones).

The product of its digits is 46656, while the sum is 40.

The square root of 21989236 is about 4689.2681731801. The cubic root of 21989236 is about 280.1582268963.

The spelling of 21989236 in words is "twenty-one million, nine hundred eighty-nine thousand, two hundred thirty-six".