21856406 has 16 divisors (see below), whose sum is σ = 38516688. Its totient is φ = 9170400.

The previous prime is 21856399. The next prime is 21856409. The reversal of 21856406 is 60465812.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21856409) 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, 37925 + ... + 38496.

It is an arithmetic number, because the mean of its divisors is an integer number (2407293).

Almost surely, 2^21856406 is an apocalyptic number.

21856406 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21856406 is a deficient number, since it is larger than the sum of its proper divisors (16660282).

21856406 is a wasteful number, since it uses less digits than its factorization.

21856406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76447.

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 21856406 is about 4675.0835286656. The cubic root of 21856406 is about 279.5929715255.

The spelling of 21856406 in words is "twenty-one million, eight hundred fifty-six thousand, four hundred six".