21012320121 has 16 divisors (see below), whose sum is σ = 30682921920. Its totient is φ = 12711493440.

The previous prime is 21012320117. The next prime is 21012320143. The reversal of 21012320121 is 12102321012.

It is not a de Polignac number, because 21012320121 - 2² = 21012320117 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21012320121.

It is not an unprimeable number, because it can be changed into a prime (21012320621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4563610 + ... + 4568211.

It is an arithmetic number, because the mean of its divisors is an integer number (1917682620).

Almost surely, 2^21012320121 is an apocalyptic number.

It is an amenable number.

21012320121 is a deficient number, since it is larger than the sum of its proper divisors (9670601799).

21012320121 is a wasteful number, since it uses less digits than its factorization.

21012320121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9131896.

The product of its (nonzero) digits is 48, while the sum is 15.

Adding to 21012320121 its reverse (12102321012), we get a palindrome (33114641133).

The spelling of 21012320121 in words is "twenty-one billion, twelve million, three hundred twenty thousand, one hundred twenty-one".