21002001 has 8 divisors (see below), whose sum is σ = 28040064. Its totient is φ = 13982640.

The previous prime is 21001991. The next prime is 21002039. The reversal of 21002001 is 10020012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21002001 - 2⁵ = 21001969 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21002081) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1801 + ... + 6726.

It is an arithmetic number, because the mean of its divisors is an integer number (3505008).

Almost surely, 2^21002001 is an apocalyptic number.

It is an amenable number.

21002001 is a deficient number, since it is larger than the sum of its proper divisors (7038063).

21002001 is an equidigital number, since it uses as much as digits as its factorization.

21002001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9351.

The product of its (nonzero) digits is 4, while the sum is 6.

The square root of 21002001 is about 4582.7940167544. The cubic root of 21002001 is about 275.9011802285.

Adding to 21002001 its reverse (10020012), we get a palindrome (31022013).

It can be divided in two parts, 2 and 1002001, that multiplied together give a palindrome (2004002).

The spelling of 21002001 in words is "twenty-one million, two thousand, one".