21090772 has 24 divisors (see below), whose sum is σ = 38543400. Its totient is φ = 10085376.

The previous prime is 21090731. The next prime is 21090791. The reversal of 21090772 is 27709012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 3147076 + 17943696 = 1774^2 + 4236^2 .

It is a super-3 number, since 3×21090772³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21090772.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12304 + ... + 13912.

It is an arithmetic number, because the mean of its divisors is an integer number (1605975).

Almost surely, 2^21090772 is an apocalyptic number.

It is an amenable number.

21090772 is a deficient number, since it is larger than the sum of its proper divisors (17452628).

21090772 is a wasteful number, since it uses less digits than its factorization.

21090772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1755 (or 1753 counting only the distinct ones).

The product of its (nonzero) digits is 1764, while the sum is 28.

The square root of 21090772 is about 4592.4690526992. The cubic root of 21090772 is about 276.2893590651.

Adding to 21090772 its reverse (27709012), we get a palindrome (48799784).

The spelling of 21090772 in words is "twenty-one million, ninety thousand, seven hundred seventy-two".