20991473684 has 6 divisors (see below), whose sum is σ = 36735078954. Its totient is φ = 10495736840.

The previous prime is 20991473663. The next prime is 20991473693. The reversal of 20991473684 is 48637419902.

It can be written as a sum of positive squares in only one way, i.e., 12494321284 + 8497152400 = 111778^2 + 92180^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2623934207 + ... + 2623934214.

It is an arithmetic number, because the mean of its divisors is an integer number (6122513159).

Almost surely, 2^20991473684 is an apocalyptic number.

It is an amenable number.

20991473684 is a deficient number, since it is larger than the sum of its proper divisors (15743605270).

20991473684 is a wasteful number, since it uses less digits than its factorization.

20991473684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5247868425 (or 5247868423 counting only the distinct ones).

The product of its (nonzero) digits is 2612736, while the sum is 53.

The spelling of 20991473684 in words is "twenty billion, nine hundred ninety-one million, four hundred seventy-three thousand, six hundred eighty-four".