21806738 has 4 divisors (see below), whose sum is σ = 32710110. Its totient is φ = 10903368.

The previous prime is 21806723. The next prime is 21806749. The reversal of 21806738 is 83760812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 15031129 + 6775609 = 3877^2 + 2603^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21806698 and 21806707.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5451683 + ... + 5451686.

Almost surely, 2^21806738 is an apocalyptic number.

21806738 is a deficient number, since it is larger than the sum of its proper divisors (10903372).

21806738 is a wasteful number, since it uses less digits than its factorization.

21806738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10903371.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21806738 is about 4669.7685167468. The cubic root of 21806738 is about 279.3810221298.

The spelling of 21806738 in words is "twenty-one million, eight hundred six thousand, seven hundred thirty-eight".