21981197 has 8 divisors (see below), whose sum is σ = 25440000. Its totient is φ = 18602064.

The previous prime is 21981191. The next prime is 21981227. The reversal of 21981197 is 79118912.

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

It is a cyclic number.

It is not a de Polignac number, because 21981197 - 2⁴ = 21981181 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21981197.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21981191) 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, 19322 + ... + 20427.

It is an arithmetic number, because the mean of its divisors is an integer number (3180000).

Almost surely, 2^21981197 is an apocalyptic number.

It is an amenable number.

21981197 is a deficient number, since it is larger than the sum of its proper divisors (3458803).

21981197 is an equidigital number, since it uses as much as digits as its factorization.

21981197 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39835.

The product of its digits is 9072, while the sum is 38.

The square root of 21981197 is about 4688.4109248230. The cubic root of 21981197 is about 280.1240819098.

The spelling of 21981197 in words is "twenty-one million, nine hundred eighty-one thousand, one hundred ninety-seven".