21555551806705 has 24 divisors (see below), whose sum is σ = 30149611515072. Its totient is φ = 14751564139872.

The previous prime is 21555551806703. The next prime is 21555551806709. The reversal of 21555551806705 is 50760815555512.

It is not a de Polignac number, because 21555551806705 - 2¹ = 21555551806703 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21555551806703) 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, 87333867 + ... + 87580336.

It is an arithmetic number, because the mean of its divisors is an integer number (1256233813128).

Almost surely, 2^{21555551806705} is an apocalyptic number.

It is an amenable number.

21555551806705 is a deficient number, since it is larger than the sum of its proper divisors (8594059708367).

21555551806705 is a wasteful number, since it uses less digits than its factorization.

21555551806705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174914725 (or 174914718 counting only the distinct ones).

The product of its (nonzero) digits is 10500000, while the sum is 55.

The spelling of 21555551806705 in words is "twenty-one trillion, five hundred fifty-five billion, five hundred fifty-one million, eight hundred six thousand, seven hundred five".