21906423 has 64 divisors (see below), whose sum is σ = 41610240. Its totient is φ = 11059200.

The previous prime is 21906413. The next prime is 21906461. The reversal of 21906423 is 32460912.

21906423 is a `hidden beast` number, since 2 + 19 + 0 + 642 + 3 = 666.

It is not a de Polignac number, because 21906423 - 2⁴ = 21906407 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906413) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 85111 + ... + 85367.

It is an arithmetic number, because the mean of its divisors is an integer number (650160).

Almost surely, 2^21906423 is an apocalyptic number.

21906423 is a deficient number, since it is larger than the sum of its proper divisors (19703817).

21906423 is a wasteful number, since it uses less digits than its factorization.

21906423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 325 (or 319 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 21906423 is about 4680.4297879575. The cubic root of 21906423 is about 279.8060859739.

The spelling of 21906423 in words is "twenty-one million, nine hundred six thousand, four hundred twenty-three".