21001212121 has 8 divisors (see below), whose sum is σ = 21108166688. Its totient is φ = 20894328000.

The previous prime is 21001212061. The next prime is 21001212143. The reversal of 21001212121 is 12121210012.

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 21001212121 - 2²³ = 20992823513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21001212161) 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, 642586 + ... + 674476.

It is an arithmetic number, because the mean of its divisors is an integer number (2638520836).

Almost surely, 2^21001212121 is an apocalyptic number.

It is an amenable number.

21001212121 is a deficient number, since it is larger than the sum of its proper divisors (106954567).

21001212121 is a wasteful number, since it uses less digits than its factorization.

21001212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35223.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21001212121 its reverse (12121210012), we get a palindrome (33122422133).

It can be divided in two parts, 210012 and 12121, that multiplied together give a palindrome (2545555452).

The spelling of 21001212121 in words is "twenty-one billion, one million, two hundred twelve thousand, one hundred twenty-one".