21457765420 has 72 divisors (see below), whose sum is σ = 56450462544. Its totient is φ = 6791025024.

The previous prime is 21457765403. The next prime is 21457765421. The reversal of 21457765420 is 2456775412.

It is not an unprimeable number, because it can be changed into a prime (21457765421) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 829402 + ... + 854881.

It is an arithmetic number, because the mean of its divisors is an integer number (784034202).

Almost surely, 2^21457765420 is an apocalyptic number.

21457765420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21457765420 is an abundant number, since it is smaller than the sum of its proper divisors (34992697124).

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

21457765420 is a wasteful number, since it uses less digits than its factorization.

21457765420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1684319 (or 1684310 counting only the distinct ones).

The product of its (nonzero) digits is 470400, while the sum is 43.

The spelling of 21457765420 in words is "twenty-one billion, four hundred fifty-seven million, seven hundred sixty-five thousand, four hundred twenty".