21406023 has 6 divisors (see below), whose sum is σ = 30919824. Its totient is φ = 14270676.

The previous prime is 21406001. The next prime is 21406037. The reversal of 21406023 is 32060412.

It is a happy number.

21406023 is a `hidden beast` number, since 21 + 40 + 602 + 3 = 666.

It is not a de Polignac number, because 21406023 - 2⁹ = 21405511 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21405987 and 21406005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21406823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1189215 + ... + 1189232.

It is an arithmetic number, because the mean of its divisors is an integer number (5153304).

Almost surely, 2^21406023 is an apocalyptic number.

21406023 is a deficient number, since it is larger than the sum of its proper divisors (9513801).

21406023 is a wasteful number, since it uses less digits than its factorization.

21406023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2378453 (or 2378450 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21406023 is about 4626.6643491829. The cubic root of 21406023 is about 277.6591538945.

Adding to 21406023 its reverse (32060412), we get a palindrome (53466435).

The spelling of 21406023 in words is "twenty-one million, four hundred six thousand, twenty-three".