21012212121 has 8 divisors (see below), whose sum is σ = 28612374144. Its totient is φ = 13710095760.

The previous prime is 21012212099. The next prime is 21012212153. The reversal of 21012212121 is 12121221012.

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

It is not a de Polignac number, because 21012212121 - 2²¹ = 21010114969 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21012212121.

It is not an unprimeable number, because it can be changed into a prime (21012232121) 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, 74511250 + ... + 74511531.

It is an arithmetic number, because the mean of its divisors is an integer number (3576546768).

Almost surely, 2^21012212121 is an apocalyptic number.

It is an amenable number.

21012212121 is a deficient number, since it is larger than the sum of its proper divisors (7600162023).

21012212121 is a wasteful number, since it uses less digits than its factorization.

21012212121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149022831.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21012212121 its reverse (12121221012), we get a palindrome (33133433133).

The spelling of 21012212121 in words is "twenty-one billion, twelve million, two hundred twelve thousand, one hundred twenty-one".