21197538 has 80 divisors (see below), whose sum is σ = 51749280. Its totient is φ = 6459264.

The previous prime is 21197489. The next prime is 21197551. The reversal of 21197538 is 83579112.

21197538 is a `hidden beast` number, since 2 + 119 + 7 + 538 = 666.

It is a super-2 number, since 2×21197538² = 898671234522888, which contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 118333 + ... + 118511.

It is an arithmetic number, because the mean of its divisors is an integer number (646866).

Almost surely, 2^21197538 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21197538, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25874640).

21197538 is an abundant number, since it is smaller than the sum of its proper divisors (30551742).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21197538 is a wasteful number, since it uses less digits than its factorization.

21197538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 253 (or 244 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21197538 is about 4604.0784094105. The cubic root of 21197538 is about 276.7547865301.

The spelling of 21197538 in words is "twenty-one million, one hundred ninety-seven thousand, five hundred thirty-eight".