21002012001 has 6 divisors (see below), whose sum is σ = 30336239570. Its totient is φ = 14001341328.

The previous prime is 21002011999. The next prime is 21002012021. The reversal of 21002012001 is 10021020012.

It can be written as a sum of positive squares in only one way, i.e., 17180917776 + 3821094225 = 131076^2 + 61815^2 .

It is not a de Polignac number, because 21002012001 - 2¹ = 21002011999 is a prime.

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: 2333556889 = 21002012001 / (2 + 1 + 0 + 0 + 2 + 0 + 1 + 2 + 0 + 0 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002012021) 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, 1166778436 + ... + 1166778453.

Almost surely, 2^21002012001 is an apocalyptic number.

It is an amenable number.

21002012001 is a deficient number, since it is larger than the sum of its proper divisors (9334227569).

21002012001 is a wasteful number, since it uses less digits than its factorization.

21002012001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2333556895 (or 2333556892 counting only the distinct ones).

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

Adding to 21002012001 its reverse (10021020012), we get a palindrome (31023032013).

The spelling of 21002012001 in words is "twenty-one billion, two million, twelve thousand, one".