21157704643 has 4 divisors (see below), whose sum is σ = 21240030600. Its totient is φ = 21075378688.

The previous prime is 21157704641. The next prime is 21157704677. The reversal of 21157704643 is 34640775112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21157704643 - 2¹ = 21157704641 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21157704596 and 21157704605.

It is not an unprimeable number, because it can be changed into a prime (21157704641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 41162593 + ... + 41163106.

It is an arithmetic number, because the mean of its divisors is an integer number (5310007650).

Almost surely, 2^21157704643 is an apocalyptic number.

21157704643 is a deficient number, since it is larger than the sum of its proper divisors (82325957).

21157704643 is an equidigital number, since it uses as much as digits as its factorization.

21157704643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82325956.

The product of its (nonzero) digits is 141120, while the sum is 40.

The spelling of 21157704643 in words is "twenty-one billion, one hundred fifty-seven million, seven hundred four thousand, six hundred forty-three".