21990001 has 12 divisors (see below), whose sum is σ = 25084080. Its totient is φ = 19116680.

The previous prime is 21989999. The next prime is 21990013. The reversal of 21990001 is 10009912.

It is not a de Polignac number, because 21990001 - 2¹ = 21989999 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21990041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3930 + ... + 7708.

It is an arithmetic number, because the mean of its divisors is an integer number (2090340).

Almost surely, 2^21990001 is an apocalyptic number.

It is an amenable number.

21990001 is a deficient number, since it is larger than the sum of its proper divisors (3094079).

21990001 is a wasteful number, since it uses less digits than its factorization.

21990001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3836 (or 3813 counting only the distinct ones).

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 21990001 is about 4689.3497417019. The cubic root of 21990001 is about 280.1614757367.

Adding to 21990001 its reverse (10009912), we get a palindrome (31999913).

The spelling of 21990001 in words is "twenty-one million, nine hundred ninety thousand, one".