21001212021 has 8 divisors (see below), whose sum is σ = 29648769984. Its totient is φ = 13177231040.

The previous prime is 21001212017. The next prime is 21001212047. The reversal of 21001212021 is 12021210012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21001212021 - 2² = 21001212017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001211988 and 21001212006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001212061) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 205894185 + ... + 205894286.

It is an arithmetic number, because the mean of its divisors is an integer number (3706096248).

Almost surely, 2^21001212021 is an apocalyptic number.

It is an amenable number.

21001212021 is a deficient number, since it is larger than the sum of its proper divisors (8647557963).

21001212021 is a wasteful number, since it uses less digits than its factorization.

21001212021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 411788491.

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

Adding to 21001212021 its reverse (12021210012), we get a palindrome (33022422033).

It can be divided in two parts, 210012 and 12021, that multiplied together give a palindrome (2524554252).

The spelling of 21001212021 in words is "twenty-one billion, one million, two hundred twelve thousand, twenty-one".