21535420640 has 24 divisors (see below), whose sum is σ = 50877431640. Its totient is φ = 8614168192.

The previous prime is 21535420637. The next prime is 21535420649. The reversal of 21535420640 is 4602453512.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 21535420597 and 21535420606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21535420649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 67298030 + ... + 67298349.

It is an arithmetic number, because the mean of its divisors is an integer number (2119892985).

Almost surely, 2^21535420640 is an apocalyptic number.

21535420640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21535420640 is an abundant number, since it is smaller than the sum of its proper divisors (29342011000).

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

21535420640 is a wasteful number, since it uses less digits than its factorization.

21535420640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134596394 (or 134596386 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 32.

The spelling of 21535420640 in words is "twenty-one billion, five hundred thirty-five million, four hundred twenty thousand, six hundred forty".