21001221201 has 16 divisors (see below), whose sum is σ = 30450104064. Its totient is φ = 12821094144.

The previous prime is 21001221181. The next prime is 21001221203. The reversal of 21001221201 is 10212210012.

It is not a de Polignac number, because 21001221201 - 2²⁷ = 20867003473 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21001221203) 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, 5562825 + ... + 5566598.

It is an arithmetic number, because the mean of its divisors is an integer number (1903131504).

Almost surely, 2^21001221201 is an apocalyptic number.

It is an amenable number.

21001221201 is a deficient number, since it is larger than the sum of its proper divisors (9448882863).

21001221201 is a wasteful number, since it uses less digits than its factorization.

21001221201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11129480.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21001221201 its reverse (10212210012), we get a palindrome (31213431213).

The spelling of 21001221201 in words is "twenty-one billion, one million, two hundred twenty-one thousand, two hundred one".