21021197 has 4 divisors (see below), whose sum is σ = 22257756. Its totient is φ = 19784640.

The previous prime is 21021181. The next prime is 21021229. The reversal of 21021197 is 79112012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6421156 + 14600041 = 2534^2 + 3821^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021197 - 2⁴ = 21021181 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021107) 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, 618254 + ... + 618287.

It is an arithmetic number, because the mean of its divisors is an integer number (5564439).

Almost surely, 2^21021197 is an apocalyptic number.

It is an amenable number.

21021197 is a deficient number, since it is larger than the sum of its proper divisors (1236559).

21021197 is a wasteful number, since it uses less digits than its factorization.

21021197 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1236558.

The product of its (nonzero) digits is 252, while the sum is 23.

The square root of 21021197 is about 4584.8878939403. The cubic root of 21021197 is about 275.9852132735.

The spelling of 21021197 in words is "twenty-one million, twenty-one thousand, one hundred ninety-seven".