21555506400 has 72 divisors (see below), whose sum is σ = 70163181144. Its totient is φ = 5748134400.

The previous prime is 21555506393. The next prime is 21555506407. The reversal of 21555506400 is 460555512.

It is an interprime number because it is at equal distance from previous prime (21555506393) and next prime (21555506407).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555506407) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4488331 + ... + 4493130.

It is an arithmetic number, because the mean of its divisors is an integer number (974488627).

Almost surely, 2^21555506400 is an apocalyptic number.

21555506400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21555506400 is an abundant number, since it is smaller than the sum of its proper divisors (48607674744).

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

21555506400 is a wasteful number, since it uses less digits than its factorization.

21555506400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8981484 (or 8981471 counting only the distinct ones).

The product of its (nonzero) digits is 30000, while the sum is 33.

The spelling of 21555506400 in words is "twenty-one billion, five hundred fifty-five million, five hundred six thousand, four hundred".