21505733387 has 2 divisors, whose sum is σ = 21505733388. Its totient is φ = 21505733386.

The previous prime is 21505733383. The next prime is 21505733411. The reversal of 21505733387 is 78333750512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21505733387 - 2² = 21505733383 is a prime.

It is not a weakly prime, because it can be changed into another prime (21505733383) 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 as a sum of consecutive naturals, namely, 10752866693 + 10752866694.

It is an arithmetic number, because the mean of its divisors is an integer number (10752866694).

Almost surely, 2^21505733387 is an apocalyptic number.

21505733387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505733387 is an equidigital number, since it uses as much as digits as its factorization.

21505733387 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 529200, while the sum is 44.

The spelling of 21505733387 in words is "twenty-one billion, five hundred five million, seven hundred thirty-three thousand, three hundred eighty-seven".