21981237 has 8 divisors (see below), whose sum is σ = 29330400. Its totient is φ = 14643120.

The previous prime is 21981229. The next prime is 21981251. The reversal of 21981237 is 73218912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21981237 - 2³ = 21981229 is a prime.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 21981198 and 21981207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5014 + ... + 8312.

It is an arithmetic number, because the mean of its divisors is an integer number (3666300).

Almost surely, 2^21981237 is an apocalyptic number.

It is an amenable number.

21981237 is a deficient number, since it is larger than the sum of its proper divisors (7349163).

21981237 is a wasteful number, since it uses less digits than its factorization.

21981237 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5523.

The product of its digits is 6048, while the sum is 33.

The square root of 21981237 is about 4688.4151906588. The cubic root of 21981237 is about 280.1242518271.

The spelling of 21981237 in words is "twenty-one million, nine hundred eighty-one thousand, two hundred thirty-seven".