21105657487 has 2 divisors, whose sum is σ = 21105657488. Its totient is φ = 21105657486.

The previous prime is 21105657457. The next prime is 21105657499. The reversal of 21105657487 is 78475650112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21105657487 - 2²⁷ = 20971439759 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21105657457) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552828743 + 10552828744.

It is an arithmetic number, because the mean of its divisors is an integer number (10552828744).

Almost surely, 2^21105657487 is an apocalyptic number.

21105657487 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105657487 is an equidigital number, since it uses as much as digits as its factorization.

21105657487 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 470400, while the sum is 46.

The spelling of 21105657487 in words is "twenty-one billion, one hundred five million, six hundred fifty-seven thousand, four hundred eighty-seven".