21181178947 has 16 divisors (see below), whose sum is σ = 22271477760. Its totient is φ = 20117462400.

The previous prime is 21181178903. The next prime is 21181178957. The reversal of 21181178947 is 74987118112.

It is a happy number.

It is not a de Polignac number, because 21181178947 - 2¹¹ = 21181176899 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21181178947.

It is not an unprimeable number, because it can be changed into a prime (21181178957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1144923 + ... + 1163275.

It is an arithmetic number, because the mean of its divisors is an integer number (1391967360).

Almost surely, 2^21181178947 is an apocalyptic number.

21181178947 is a deficient number, since it is larger than the sum of its proper divisors (1090298813).

21181178947 is a wasteful number, since it uses less digits than its factorization.

21181178947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19074.

The product of its digits is 225792, while the sum is 49.

The spelling of 21181178947 in words is "twenty-one billion, one hundred eighty-one million, one hundred seventy-eight thousand, nine hundred forty-seven".