21005722 has 8 divisors (see below), whose sum is σ = 31720500. Its totient is φ = 10432224.

The previous prime is 21005713. The next prime is 21005737. The reversal of 21005722 is 22750012.

It can be written as a sum of positive squares in 2 ways, for example, as 16248961 + 4756761 = 4031^2 + 2181^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 21005722.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 34947 + ... + 35542.

Almost surely, 2^21005722 is an apocalyptic number.

21005722 is a deficient number, since it is larger than the sum of its proper divisors (10714778).

21005722 is a wasteful number, since it uses less digits than its factorization.

21005722 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70640.

The product of its (nonzero) digits is 280, while the sum is 19.

The square root of 21005722 is about 4583.1999738174. The cubic root of 21005722 is about 275.9174734009.

Adding to 21005722 its reverse (22750012), we get a palindrome (43755734).

The spelling of 21005722 in words is "twenty-one million, five thousand, seven hundred twenty-two".