21123210010121 has 4 divisors (see below), whose sum is σ = 21123229360452. Its totient is φ = 21123190659792.

The previous prime is 21123210010103. The next prime is 21123210010193. The reversal of 21123210010121 is 12101001232112.

It is a happy number.

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 7076605515721 + 14046604494400 = 2660189^2 + 3747880^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123210010121 - 2⁶ = 21123210010057 is a prime.

It is a super-2 number, since 2×21123210010121² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21123210010121.

It is not an unprimeable number, because it can be changed into a prime (21123210010421) 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, 7933190 + ... + 10255823.

It is an arithmetic number, because the mean of its divisors is an integer number (5280807340113).

Almost surely, 2^{21123210010121} is an apocalyptic number.

It is an amenable number.

21123210010121 is a deficient number, since it is larger than the sum of its proper divisors (19350331).

21123210010121 is a wasteful number, since it uses less digits than its factorization.

21123210010121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19350330.

The product of its (nonzero) digits is 48, while the sum is 17.

Adding to 21123210010121 its reverse (12101001232112), we get a palindrome (33224211242233).

The spelling of 21123210010121 in words is "twenty-one trillion, one hundred twenty-three billion, two hundred ten million, ten thousand, one hundred twenty-one".