21726406 has 16 divisors (see below), whose sum is σ = 35580384. Its totient is φ = 9889344.

The previous prime is 21726403. The next prime is 21726427. The reversal of 21726406 is 60462712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21726401) 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 7 ways as a sum of consecutive naturals, for example, 3826 + ... + 7621.

It is an arithmetic number, because the mean of its divisors is an integer number (2223774).

Almost surely, 2^21726406 is an apocalyptic number.

21726406 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21726406 is a deficient number, since it is larger than the sum of its proper divisors (13853978).

21726406 is a wasteful number, since it uses less digits than its factorization.

21726406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11535.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 21726406 is about 4661.1592978571. The cubic root of 21726406 is about 279.0375372900.

It can be divided in two parts, 21 and 726406, that multiplied together give a triangular number (15254526 = T₅₅₂₃).

The spelling of 21726406 in words is "twenty-one million, seven hundred twenty-six thousand, four hundred six".