21397001 has 4 divisors (see below), whose sum is σ = 21800772. Its totient is φ = 20993232.

The previous prime is 21396967. The next prime is 21397007. The reversal of 21397001 is 10079312.

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 14899600 + 6497401 = 3860^2 + 2549^2 .

It is a cyclic number.

It is not a de Polignac number, because 21397001 - 2¹⁸ = 21134857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21397007) 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, 201806 + ... + 201911.

It is an arithmetic number, because the mean of its divisors is an integer number (5450193).

Almost surely, 2^21397001 is an apocalyptic number.

It is an amenable number.

21397001 is a deficient number, since it is larger than the sum of its proper divisors (403771).

21397001 is an equidigital number, since it uses as much as digits as its factorization.

21397001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 403770.

The product of its (nonzero) digits is 378, while the sum is 23.

The square root of 21397001 is about 4625.6892459395. The cubic root of 21397001 is about 277.6201400634.

The spelling of 21397001 in words is "twenty-one million, three hundred ninety-seven thousand, one".