21172197 has 8 divisors (see below), whose sum is σ = 28493856. Its totient is φ = 13982672.

The previous prime is 21172189. The next prime is 21172223. The reversal of 21172197 is 79127112.

It is a happy number.

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 21172197 - 2³ = 21172189 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172147) 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, 32658 + ... + 33299.

It is an arithmetic number, because the mean of its divisors is an integer number (3561732).

Almost surely, 2^21172197 is an apocalyptic number.

It is an amenable number.

21172197 is a deficient number, since it is larger than the sum of its proper divisors (7321659).

21172197 is a wasteful number, since it uses less digits than its factorization.

21172197 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66067.

The product of its digits is 1764, while the sum is 30.

The square root of 21172197 is about 4601.3255698766. The cubic root of 21172197 is about 276.6444586293.

The spelling of 21172197 in words is "twenty-one million, one hundred seventy-two thousand, one hundred ninety-seven".