21906456 has 96 divisors (see below), whose sum is σ = 64825920. Its totient is φ = 6115200.

The previous prime is 21906413. The next prime is 21906461. The reversal of 21906456 is 65460912.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 44371 + ... + 44861.

It is an arithmetic number, because the mean of its divisors is an integer number (675270).

Almost surely, 2^21906456 is an apocalyptic number.

21906456 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21906456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32412960).

21906456 is an abundant number, since it is smaller than the sum of its proper divisors (42919464).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21906456 is a wasteful number, since it uses less digits than its factorization.

21906456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 537 (or 520 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 33.

The square root of 21906456 is about 4680.4333132735. The cubic root of 21906456 is about 279.8062264745.

It can be divided in two parts, 2190 and 6456, that added together give a triangular number (8646 = T₁₃₁).

The spelling of 21906456 in words is "twenty-one million, nine hundred six thousand, four hundred fifty-six".