21403723 has 16 divisors (see below), whose sum is σ = 24558336. Its totient is φ = 18476640.

The previous prime is 21403721. The next prime is 21403727. The reversal of 21403723 is 32730412.

It is a cyclic number.

It is not a de Polignac number, because 21403723 - 2¹ = 21403721 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21403694 and 21403703.

It is not an unprimeable number, because it can be changed into a prime (21403721) 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 15 ways as a sum of consecutive naturals, for example, 16890 + ... + 18112.

It is an arithmetic number, because the mean of its divisors is an integer number (1534896).

Almost surely, 2^21403723 is an apocalyptic number.

21403723 is a deficient number, since it is larger than the sum of its proper divisors (3154613).

21403723 is a wasteful number, since it uses less digits than its factorization.

21403723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1314.

The product of its (nonzero) digits is 1008, while the sum is 22.

The square root of 21403723 is about 4626.4157833035. The cubic root of 21403723 is about 277.6492090467.

The spelling of 21403723 in words is "twenty-one million, four hundred three thousand, seven hundred twenty-three".