21012001 has 4 divisors (see below), whose sum is σ = 21080752.
Its totient is φ = 20943252.
The previous prime is 21011981. The next prime is 21012053. The reversal of 21012001 is 10021012.
Adding to 21012001 its reverse (10021012), we get a palindrome (31033013).
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 21012001 - 27 = 21011873 is a prime.
It is a Duffinian number.
It is not an unprimeable number, because it can be changed into a prime (21012091) 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, 33915 + ... + 34528.
It is an arithmetic number, because the mean of its divisors is an integer number (5270188).
Almost surely, 221012001 is an apocalyptic number.
It is an amenable number.
21012001 is a deficient number, since it is larger than the sum of its proper divisors (68751).
21012001 is an equidigital number, since it uses as much as digits as its factorization.
21012001 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 68750.
The product of its (nonzero) digits is 4, while the sum is 7.
The square root of 21012001 is about 4583.8849243846.
The cubic root of 21012001 is about 275.9449629459.
The spelling of 21012001 in words is "twenty-one million, twelve thousand, one".