21636421487 has 4 divisors (see below), whose sum is σ = 21910300320. Its totient is φ = 21362542656.

The previous prime is 21636421483. The next prime is 21636421519. The reversal of 21636421487 is 78412463612.

It is a happy number.

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 21636421487 - 2² = 21636421483 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 (21636421481) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136939298 + ... + 136939455.

It is an arithmetic number, because the mean of its divisors is an integer number (5477575080).

Almost surely, 2^21636421487 is an apocalyptic number.

21636421487 is a deficient number, since it is larger than the sum of its proper divisors (273878833).

21636421487 is an equidigital number, since it uses as much as digits as its factorization.

21636421487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273878832.

The product of its digits is 387072, while the sum is 44.

The spelling of 21636421487 in words is "twenty-one billion, six hundred thirty-six million, four hundred twenty-one thousand, four hundred eighty-seven".