21001213123 has 16 divisors (see below), whose sum is σ = 23261056992. Its totient is φ = 18800640000.

The previous prime is 21001213117. The next prime is 21001213147. The reversal of 21001213123 is 32131210012.

It is a cyclic number.

It is not a de Polignac number, because 21001213123 - 2⁹ = 21001212611 is a prime.

It is a super-3 number, since 3×21001213123³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001213097 and 21001213106.

It is not an unprimeable number, because it can be changed into a prime (21001213153) 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, 494323 + ... + 535123.

It is an arithmetic number, because the mean of its divisors is an integer number (1453816062).

Almost surely, 2^21001213123 is an apocalyptic number.

21001213123 is a deficient number, since it is larger than the sum of its proper divisors (2259843869).

21001213123 is a wasteful number, since it uses less digits than its factorization.

21001213123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41526.

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 21001213123 its reverse (32131210012), we get a palindrome (53132423135).

The spelling of 21001213123 in words is "twenty-one billion, one million, two hundred thirteen thousand, one hundred twenty-three".