21851423 has 16 divisors (see below), whose sum is σ = 24968736. Its totient is φ = 18944640.

The previous prime is 21851419. The next prime is 21851441. The reversal of 21851423 is 32415812.

It is not a de Polignac number, because 21851423 - 2² = 21851419 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21851392 and 21851401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21851023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21065 + ... + 22077.

It is an arithmetic number, because the mean of its divisors is an integer number (1560546).

Almost surely, 2^21851423 is an apocalyptic number.

21851423 is a deficient number, since it is larger than the sum of its proper divisors (3117313).

21851423 is a wasteful number, since it uses less digits than its factorization.

21851423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1114.

The product of its digits is 1920, while the sum is 26.

The square root of 21851423 is about 4674.5505666320. The cubic root of 21851423 is about 279.5717219558.

The spelling of 21851423 in words is "twenty-one million, eight hundred fifty-one thousand, four hundred twenty-three".