21001022001 has 6 divisors (see below), whose sum is σ = 30334809570. Its totient is φ = 14000681328.

The previous prime is 21001021991. The next prime is 21001022033. The reversal of 21001022001 is 10022010012.

It can be written as a sum of positive squares in only one way, i.e., 14791424400 + 6209597601 = 121620^2 + 78801^2 .

It is not a de Polignac number, because 21001022001 - 2⁵ = 21001021969 is a prime.

It is a super-3 number, since 3×21001022001³ (a number of 32 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (9), and also a Moran number because the ratio is a prime number: 2333446889 = 21001022001 / (2 + 1 + 0 + 0 + 1 + 0 + 2 + 2 + 0 + 0 + 1).

It is not an unprimeable number, because it can be changed into a prime (21001022071) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1166723436 + ... + 1166723453.

It is an arithmetic number, because the mean of its divisors is an integer number (5055801595).

Almost surely, 2^21001022001 is an apocalyptic number.

It is an amenable number.

21001022001 is a deficient number, since it is larger than the sum of its proper divisors (9333787569).

21001022001 is a wasteful number, since it uses less digits than its factorization.

21001022001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2333446895 (or 2333446892 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21001022001 its reverse (10022010012), we get a palindrome (31023032013).

The spelling of 21001022001 in words is "twenty-one billion, one million, twenty-two thousand, one".