21021220001 has 16 divisors (see below), whose sum is σ = 23974714368. Its totient is φ = 18313996800.

The previous prime is 21021219883. The next prime is 21021220007. The reversal of 21021220001 is 10002212012.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21021220001 - 2¹⁴ = 21021203617 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21021220007) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 855020 + ... + 879261.

It is an arithmetic number, because the mean of its divisors is an integer number (1498419648).

Almost surely, 2^21021220001 is an apocalyptic number.

It is an amenable number.

21021220001 is a deficient number, since it is larger than the sum of its proper divisors (2953494367).

21021220001 is a wasteful number, since it uses less digits than its factorization.

21021220001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1734352.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21021220001 its reverse (10002212012), we get a palindrome (31023432013).

The spelling of 21021220001 in words is "twenty-one billion, twenty-one million, two hundred twenty thousand, one".