21020001 has 4 divisors (see below), whose sum is σ = 28026672. Its totient is φ = 14013332.

The previous prime is 21019993. The next prime is 21020011. The reversal of 21020001 is 10002012.

It is a happy 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 21020001 - 2³ = 21019993 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21020011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3503331 + ... + 3503336.

It is an arithmetic number, because the mean of its divisors is an integer number (7006668).

Almost surely, 2^21020001 is an apocalyptic number.

It is an amenable number.

21020001 is a deficient number, since it is larger than the sum of its proper divisors (7006671).

21020001 is an equidigital number, since it uses as much as digits as its factorization.

21020001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7006670.

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

The square root of 21020001 is about 4584.7574635961. The cubic root of 21020001 is about 275.9799791190.

Adding to 21020001 its reverse (10002012), we get a palindrome (31022013).

The spelling of 21020001 in words is "twenty-one million, twenty thousand, one".