21061644 has 24 divisors (see below), whose sum is σ = 49278768. Its totient is φ = 7001280.

The previous prime is 21061639. The next prime is 21061669. The reversal of 21061644 is 44616012.

It is a super-3 number, since 3×21061644³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2554 + ... + 6974.

It is an arithmetic number, because the mean of its divisors is an integer number (2053282).

Almost surely, 2^21061644 is an apocalyptic number.

It is an amenable number.

21061644 is an abundant number, since it is smaller than the sum of its proper divisors (28217124).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21061644 is a wasteful number, since it uses less digits than its factorization.

21061644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4825 (or 4823 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21061644 is about 4589.2966781414. The cubic root of 21061644 is about 276.1621080861.

Adding to 21061644 its reverse (44616012), we get a palindrome (65677656).

The spelling of 21061644 in words is "twenty-one million, sixty-one thousand, six hundred forty-four".