21205355440 has 80 divisors (see below), whose sum is σ = 49634323200. Its totient is φ = 8425230336.

The previous prime is 21205355429. The next prime is 21205355453. The reversal of 21205355440 is 4455350212.

It is a tau number, because it is divible by the number of its divisors (80).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10149916 + ... + 10152004.

It is an arithmetic number, because the mean of its divisors is an integer number (620429040).

Almost surely, 2^21205355440 is an apocalyptic number.

21205355440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21205355440 is an abundant number, since it is smaller than the sum of its proper divisors (28428967760).

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

21205355440 is a wasteful number, since it uses less digits than its factorization.

21205355440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2894 (or 2888 counting only the distinct ones).

The product of its (nonzero) digits is 24000, while the sum is 31.

The spelling of 21205355440 in words is "twenty-one billion, two hundred five million, three hundred fifty-five thousand, four hundred forty".