21000401 has 4 divisors (see below), whose sum is σ = 21356400. Its totient is φ = 20644404.

The previous prime is 21000391. The next prime is 21000407. The reversal of 21000401 is 10400012.

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 21000401 - 2⁶ = 21000337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21000407) 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, 177911 + ... + 178028.

It is an arithmetic number, because the mean of its divisors is an integer number (5339100).

Almost surely, 2^21000401 is an apocalyptic number.

It is an amenable number.

21000401 is a deficient number, since it is larger than the sum of its proper divisors (355999).

21000401 is an equidigital number, since it uses as much as digits as its factorization.

21000401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 355998.

The product of its (nonzero) digits is 8, while the sum is 8.

The square root of 21000401 is about 4582.6194474340. The cubic root of 21000401 is about 275.8941737041.

Adding to 21000401 its reverse (10400012), we get a palindrome (31400413).

The spelling of 21000401 in words is "twenty-one million, four hundred one", and thus it is an aban number.