21781612854 has 16 divisors (see below), whose sum is σ = 48403584240. Its totient is φ = 7260537600.

The previous prime is 21781612849. The next prime is 21781612877. The reversal of 21781612854 is 45821618712.

21781612854 is a `hidden beast` number, since 21 + 7 + 8 + 1 + 612 + 8 + 5 + 4 = 666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 201681547 + ... + 201681654.

It is an arithmetic number, because the mean of its divisors is an integer number (3025224015).

Almost surely, 2^21781612854 is an apocalyptic number.

21781612854 is an abundant number, since it is smaller than the sum of its proper divisors (26621971386).

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

21781612854 is a wasteful number, since it uses less digits than its factorization.

21781612854 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 403363212 (or 403363206 counting only the distinct ones).

The product of its digits is 215040, while the sum is 45.

The spelling of 21781612854 in words is "twenty-one billion, seven hundred eighty-one million, six hundred twelve thousand, eight hundred fifty-four".