21105001 has 4 divisors (see below), whose sum is σ = 21302352. Its totient is φ = 20907652.

The previous prime is 21104999. The next prime is 21105013. The reversal of 21105001 is 10050112.

It is a happy number.

It is the 1876-th star number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21105001 - 2¹ = 21104999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21105401) 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, 98515 + ... + 98728.

It is an arithmetic number, because the mean of its divisors is an integer number (5325588).

Almost surely, 2^21105001 is an apocalyptic number.

It is an amenable number.

21105001 is a deficient number, since it is larger than the sum of its proper divisors (197351).

21105001 is a wasteful number, since it uses less digits than its factorization.

21105001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 197350.

The product of its (nonzero) digits is 10, while the sum is 10.

The square root of 21105001 is about 4594.0179581713. The cubic root of 21105001 is about 276.3514784528.

Adding to 21105001 its reverse (10050112), we get a palindrome (31155113).

The spelling of 21105001 in words is "twenty-one million, one hundred five thousand, one".