21351555505 has 32 divisors (see below), whose sum is σ = 30869913600. Its totient is φ = 13867277760.

The previous prime is 21351555503. The next prime is 21351555509. The reversal of 21351555505 is 50555515312.

It is not a de Polignac number, because 21351555505 - 2¹ = 21351555503 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21351555503) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 158355 + ... + 260344.

It is an arithmetic number, because the mean of its divisors is an integer number (964684800).

Almost surely, 2^21351555505 is an apocalyptic number.

It is an amenable number.

21351555505 is a deficient number, since it is larger than the sum of its proper divisors (9518358095).

21351555505 is a wasteful number, since it uses less digits than its factorization.

21351555505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 418789.

The product of its (nonzero) digits is 93750, while the sum is 37.

The spelling of 21351555505 in words is "twenty-one billion, three hundred fifty-one million, five hundred fifty-five thousand, five hundred five".