21605722 has 8 divisors (see below), whose sum is σ = 32645556. Its totient is φ = 10723872.

The previous prime is 21605711. The next prime is 21605747. The reversal of 21605722 is 22750612.

It can be written as a sum of positive squares in 2 ways, for example, as 20331081 + 1274641 = 4509^2 + 1129^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

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 in 3 ways as a sum of consecutive naturals, for example, 39153 + ... + 39700.

Almost surely, 2^21605722 is an apocalyptic number.

21605722 is a deficient number, since it is larger than the sum of its proper divisors (11039834).

21605722 is a wasteful number, since it uses less digits than its factorization.

21605722 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78992.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21605722 is about 4648.1955638721. The cubic root of 21605722 is about 278.5199196709.

The spelling of 21605722 in words is "twenty-one million, six hundred five thousand, seven hundred twenty-two".