21081685042 has 16 divisors (see below), whose sum is σ = 34782408864. Its totient is φ = 9582582900.

The previous prime is 21081685019. The next prime is 21081685063. The reversal of 21081685042 is 24058618012.

It is a junction number, because it is equal to n+sod(n) for n = 21081684992 and 21081685010.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3957084 + ... + 3962407.

It is an arithmetic number, because the mean of its divisors is an integer number (2173900554).

Almost surely, 2^21081685042 is an apocalyptic number.

21081685042 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21081685042 is a deficient number, since it is larger than the sum of its proper divisors (13700723822).

21081685042 is an equidigital number, since it uses as much as digits as its factorization.

21081685042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7919526 (or 7919504 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 37.

The spelling of 21081685042 in words is "twenty-one billion, eighty-one million, six hundred eighty-five thousand, forty-two".