21210212101 has 4 divisors (see below), whose sum is σ = 22841766892. Its totient is φ = 19578657312.

The previous prime is 21210212083. The next prime is 21210212137. The reversal of 21210212101 is 10121201212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13706321476 + 7503890625 = 117074^2 + 86625^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210212101 - 2¹¹ = 21210210053 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13), and also a Moran number because the ratio is a prime number: 1631554777 = 21210212101 / (2 + 1 + 2 + 1 + 0 + 2 + 1 + 2 + 1 + 0 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210212171) 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, 815777376 + ... + 815777401.

It is an arithmetic number, because the mean of its divisors is an integer number (5710441723).

Almost surely, 2^21210212101 is an apocalyptic number.

It is an amenable number.

21210212101 is a deficient number, since it is larger than the sum of its proper divisors (1631554791).

21210212101 is a wasteful number, since it uses less digits than its factorization.

21210212101 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1631554790.

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

Adding to 21210212101 its reverse (10121201212), we get a palindrome (31331413313).

The spelling of 21210212101 in words is "twenty-one billion, two hundred ten million, two hundred twelve thousand, one hundred one".