21155572 has 6 divisors (see below), whose sum is σ = 37022258. Its totient is φ = 10577784.

The previous prime is 21155551. The next prime is 21155591. The reversal of 21155572 is 27555112.

It can be written as a sum of positive squares in only one way, i.e., 17673616 + 3481956 = 4204^2 + 1866^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21155572.

It is a congruent number.

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, 2644443 + ... + 2644450.

Almost surely, 2^21155572 is an apocalyptic number.

It is an amenable number.

21155572 is a deficient number, since it is larger than the sum of its proper divisors (15866686).

21155572 is a wasteful number, since it uses less digits than its factorization.

21155572 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5288897 (or 5288895 counting only the distinct ones).

The product of its digits is 3500, while the sum is 28.

The square root of 21155572 is about 4599.5186704698. The cubic root of 21155572 is about 276.5720300184.

The spelling of 21155572 in words is "twenty-one million, one hundred fifty-five thousand, five hundred seventy-two".