21152215555 has 4 divisors (see below), whose sum is σ = 25382658672. Its totient is φ = 16921772440.

The previous prime is 21152215549. The next prime is 21152215583. The reversal of 21152215555 is 55551225112.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21152215555 - 2⁹ = 21152215043 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21152215555.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2115221551 + ... + 2115221560.

It is an arithmetic number, because the mean of its divisors is an integer number (6345664668).

Almost surely, 2^21152215555 is an apocalyptic number.

21152215555 is a deficient number, since it is larger than the sum of its proper divisors (4230443117).

21152215555 is an equidigital number, since it uses as much as digits as its factorization.

21152215555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4230443116.

The product of its digits is 25000, while the sum is 34.

The spelling of 21152215555 in words is "twenty-one billion, one hundred fifty-two million, two hundred fifteen thousand, five hundred fifty-five".