21021002001 has 6 divisors (see below), whose sum is σ = 30363669570. Its totient is φ = 14014001328.

The previous prime is 21021001999. The next prime is 21021002003. The reversal of 21021002001 is 10020012012.

It is an interprime number because it is at equal distance from previous prime (21021001999) and next prime (21021002003).

It can be written as a sum of positive squares in only one way, i.e., 20857136400 + 163865601 = 144420^2 + 12801^2 .

It is not a de Polignac number, because 21021002001 - 2¹ = 21021001999 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: 2335666889 = 21021002001 / (2 + 1 + 0 + 2 + 1 + 0 + 0 + 2 + 0 + 0 + 1).

It is not an unprimeable number, because it can be changed into a prime (21021002003) 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, 1167833436 + ... + 1167833453.

It is an arithmetic number, because the mean of its divisors is an integer number (5060611595).

Almost surely, 2^21021002001 is an apocalyptic number.

It is an amenable number.

21021002001 is a deficient number, since it is larger than the sum of its proper divisors (9342667569).

21021002001 is a wasteful number, since it uses less digits than its factorization.

21021002001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2335666895 (or 2335666892 counting only the distinct ones).

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

Adding to 21021002001 its reverse (10020012012), we get a palindrome (31041014013).

The spelling of 21021002001 in words is "twenty-one billion, twenty-one million, two thousand, one".