21015533887 has 2 divisors, whose sum is σ = 21015533888. Its totient is φ = 21015533886.

The previous prime is 21015533881. The next prime is 21015533989. The reversal of 21015533887 is 78833551012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21015533887 - 2³ = 21015533879 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21015533881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10507766943 + 10507766944.

It is an arithmetic number, because the mean of its divisors is an integer number (10507766944).

Almost surely, 2^21015533887 is an apocalyptic number.

21015533887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015533887 is an equidigital number, since it uses as much as digits as its factorization.

21015533887 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 201600, while the sum is 43.

The spelling of 21015533887 in words is "twenty-one billion, fifteen million, five hundred thirty-three thousand, eight hundred eighty-seven".