21045001 has 4 divisors (see below), whose sum is σ = 21723904. Its totient is φ = 20366100.

The previous prime is 21044999. The next prime is 21045041. The reversal of 21045001 is 10054012.

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 21045001 - 2¹ = 21044999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21045041) 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, 339405 + ... + 339466.

It is an arithmetic number, because the mean of its divisors is an integer number (5430976).

Almost surely, 2^21045001 is an apocalyptic number.

It is an amenable number.

21045001 is a deficient number, since it is larger than the sum of its proper divisors (678903).

21045001 is an equidigital number, since it uses as much as digits as its factorization.

21045001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 678902.

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21045001 is about 4587.4830789879. The cubic root of 21045001 is about 276.0893474296.

Adding to 21045001 its reverse (10054012), we get a palindrome (31099013).

The spelling of 21045001 in words is "twenty-one million, forty-five thousand, one".