21105772 has 12 divisors (see below), whose sum is σ = 39107880. Its totient is φ = 9932096.

The previous prime is 21105769. The next prime is 21105781. The reversal of 21105772 is 27750112.

It is a happy number.

It is a super-2 number, since 2×21105772² = 890907223431968, which contains 22 as substring.

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, 155122 + ... + 155257.

It is an arithmetic number, because the mean of its divisors is an integer number (3258990).

Almost surely, 2^21105772 is an apocalyptic number.

It is an amenable number.

21105772 is a deficient number, since it is larger than the sum of its proper divisors (18002108).

21105772 is a wasteful number, since it uses less digits than its factorization.

21105772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310400 (or 310398 counting only the distinct ones).

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 21105772 is about 4594.1018708775. The cubic root of 21105772 is about 276.3548436014.

Adding to 21105772 its reverse (27750112), we get a palindrome (48855884).

The spelling of 21105772 in words is "twenty-one million, one hundred five thousand, seven hundred seventy-two".