21123001 has 4 divisors (see below), whose sum is σ = 21316900. Its totient is φ = 20929104.

The previous prime is 21122971. The next prime is 21123013. The reversal of 21123001 is 10032112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7284601 + 13838400 = 2699^2 + 3720^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123001 - 2¹³ = 21114809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21123301) 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 3 ways as a sum of consecutive naturals, for example, 96786 + ... + 97003.

It is an arithmetic number, because the mean of its divisors is an integer number (5329225).

Almost surely, 2^21123001 is an apocalyptic number.

It is an amenable number.

21123001 is a deficient number, since it is larger than the sum of its proper divisors (193899).

21123001 is a wasteful number, since it uses less digits than its factorization.

21123001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 193898.

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21123001 is about 4595.9766100362. The cubic root of 21123001 is about 276.4300208658.

Adding to 21123001 its reverse (10032112), we get a palindrome (31155113).

The spelling of 21123001 in words is "twenty-one million, one hundred twenty-three thousand, one".