21012123 has 8 divisors (see below), whose sum is σ = 30563136. Its totient is φ = 12734600.

The previous prime is 21012091. The next prime is 21012127. The reversal of 21012123 is 32121012.

21012123 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

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

It is a cyclic number.

It is not a de Polignac number, because 21012123 - 2⁵ = 21012091 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21012099 and 21012108.

It is not an unprimeable number, because it can be changed into a prime (21012127) 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, 318333 + ... + 318398.

It is an arithmetic number, because the mean of its divisors is an integer number (3820392).

Almost surely, 2^21012123 is an apocalyptic number.

21012123 is a deficient number, since it is larger than the sum of its proper divisors (9551013).

21012123 is a wasteful number, since it uses less digits than its factorization.

21012123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 636745.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21012123 is about 4583.8982318546. The cubic root of 21012123 is about 275.9454970092.

Adding to 21012123 its reverse (32121012), we get a palindrome (53133135).

Subtracting 21012123 from its reverse (32121012), we obtain a square (11108889 = 3333²).

It can be divided in two parts, 2101 and 2123, that added together give a palindrome (4224).

The spelling of 21012123 in words is "twenty-one million, twelve thousand, one hundred twenty-three".