21181649 has 16 divisors (see below), whose sum is σ = 22909440. Its totient is φ = 19543680.

The previous prime is 21181627. The next prime is 21181651. The reversal of 21181649 is 94618112.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21181649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21181669) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 67517 + ... + 67829.

It is an arithmetic number, because the mean of its divisors is an integer number (1431840).

Almost surely, 2^21181649 is an apocalyptic number.

It is an amenable number.

21181649 is a deficient number, since it is larger than the sum of its proper divisors (1727791).

21181649 is a wasteful number, since it uses less digits than its factorization.

21181649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 440.

The product of its digits is 3456, while the sum is 32.

The square root of 21181649 is about 4602.3525505984. The cubic root of 21181649 is about 276.6856203850.

The spelling of 21181649 in words is "twenty-one million, one hundred eighty-one thousand, six hundred forty-nine".