21102001 has 4 divisors (see below), whose sum is σ = 21125232. Its totient is φ = 21078772.

The previous prime is 21101963. The next prime is 21102023. The reversal of 21102001 is 10020112.

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 a de Polignac number, because none of the positive numbers 2^k-21102001 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a zygodrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21102071) 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, 10195 + ... + 12088.

It is an arithmetic number, because the mean of its divisors is an integer number (5281308).

Almost surely, 2^21102001 is an apocalyptic number.

It is an amenable number.

21102001 is a deficient number, since it is larger than the sum of its proper divisors (23231).

21102001 is an equidigital number, since it uses as much as digits as its factorization.

21102001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23230.

The product of its (nonzero) digits is 4, while the sum is 7.

The square root of 21102001 is about 4593.6914350008. The cubic root of 21102001 is about 276.3383837093.

Adding to 21102001 its reverse (10020112), we get a palindrome (31122113).

The spelling of 21102001 in words is "twenty-one million, one hundred two thousand, one".