21201212001 has 4 divisors (see below), whose sum is σ = 28268282672. Its totient is φ = 14134141332.

The previous prime is 21201211991. The next prime is 21201212009. The reversal of 21201212001 is 10021210212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21201212001 - 2⁷ = 21201211873 is a prime.

It is a super-2 number, since 2×21201212001² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21201212009) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3533535331 + ... + 3533535336.

It is an arithmetic number, because the mean of its divisors is an integer number (7067070668).

Almost surely, 2^21201212001 is an apocalyptic number.

It is an amenable number.

21201212001 is a deficient number, since it is larger than the sum of its proper divisors (7067070671).

21201212001 is an equidigital number, since it uses as much as digits as its factorization.

21201212001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7067070670.

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

Adding to 21201212001 its reverse (10021210212), we get a palindrome (31222422213).

It can be divided in two parts, 2120 and 1212001, that added together give a palindrome (1214121).

The spelling of 21201212001 in words is "twenty-one billion, two hundred one million, two hundred twelve thousand, one".