21257835780 has 48 divisors (see below), whose sum is σ = 61574425920. Its totient is φ = 5473281408.

The previous prime is 21257835779. The next prime is 21257835787. The reversal of 21257835780 is 8753875212.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21257835787) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6106834 + ... + 6110313.

It is an arithmetic number, because the mean of its divisors is an integer number (1282800540).

Almost surely, 2^21257835780 is an apocalyptic number.

21257835780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21257835780 is an abundant number, since it is smaller than the sum of its proper divisors (40316590140).

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

21257835780 is a wasteful number, since it uses less digits than its factorization.

21257835780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12217188 (or 12217186 counting only the distinct ones).

The product of its (nonzero) digits is 940800, while the sum is 48.

The spelling of 21257835780 in words is "twenty-one billion, two hundred fifty-seven million, eight hundred thirty-five thousand, seven hundred eighty".