21105657499 has 2 divisors, whose sum is σ = 21105657500. Its totient is φ = 21105657498.

The previous prime is 21105657487. The next prime is 21105657523. The reversal of 21105657499 is 99475650112.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21105657499 - 2¹¹ = 21105655451 is a prime.

It is not a weakly prime, because it can be changed into another prime (21105652499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552828749 + 10552828750.

It is an arithmetic number, because the mean of its divisors is an integer number (10552828750).

Almost surely, 2^21105657499 is an apocalyptic number.

21105657499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105657499 is an equidigital number, since it uses as much as digits as its factorization.

21105657499 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 680400, while the sum is 49.

The spelling of 21105657499 in words is "twenty-one billion, one hundred five million, six hundred fifty-seven thousand, four hundred ninety-nine".