21545415887 has 4 divisors (see below), whose sum is σ = 21545991096. Its totient is φ = 21544840680.

The previous prime is 21545415863. The next prime is 21545415901. The reversal of 21545415887 is 78851454512.

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

It is a cyclic number.

It is not a de Polignac number, because 21545415887 - 2²⁴ = 21528638671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21545415487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 227189 + ... + 307742.

It is an arithmetic number, because the mean of its divisors is an integer number (5386497774).

Almost surely, 2^21545415887 is an apocalyptic number.

21545415887 is a deficient number, since it is larger than the sum of its proper divisors (575209).

21545415887 is an equidigital number, since it uses as much as digits as its factorization.

21545415887 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 575208.

The product of its digits is 1792000, while the sum is 50.

The spelling of 21545415887 in words is "twenty-one billion, five hundred forty-five million, four hundred fifteen thousand, eight hundred eighty-seven".