21805957578 has 16 divisors (see below), whose sum is σ = 44035333056. Its totient is φ = 7198082880.

The previous prime is 21805957577. The next prime is 21805957583. The reversal of 21805957578 is 87575950812.

It is not an unprimeable number, because it can be changed into a prime (21805957571) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17641743 + ... + 17642978.

It is an arithmetic number, because the mean of its divisors is an integer number (2752208316).

Almost surely, 2^21805957578 is an apocalyptic number.

21805957578 is an abundant number, since it is smaller than the sum of its proper divisors (22229375478).

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

21805957578 is a wasteful number, since it uses less digits than its factorization.

21805957578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35284829.

The product of its (nonzero) digits is 7056000, while the sum is 57.

The spelling of 21805957578 in words is "twenty-one billion, eight hundred five million, nine hundred fifty-seven thousand, five hundred seventy-eight".