21057720487 has 2 divisors, whose sum is σ = 21057720488. Its totient is φ = 21057720486.

The previous prime is 21057720479. The next prime is 21057720511. The reversal of 21057720487 is 78402775012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21057720487 - 2³ = 21057720479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21057720427) 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, 10528860243 + 10528860244.

It is an arithmetic number, because the mean of its divisors is an integer number (10528860244).

Almost surely, 2^21057720487 is an apocalyptic number.

21057720487 is a deficient number, since it is larger than the sum of its proper divisors (1).

21057720487 is an equidigital number, since it uses as much as digits as its factorization.

21057720487 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 219520, while the sum is 43.

The spelling of 21057720487 in words is "twenty-one billion, fifty-seven million, seven hundred twenty thousand, four hundred eighty-seven".