21691464523 has 4 divisors (see below), whose sum is σ = 21700709080. Its totient is φ = 21682219968.

The previous prime is 21691464521. The next prime is 21691464643. The reversal of 21691464523 is 32546419612.

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 21691464523 - 2¹ = 21691464521 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21691464523.

It is not an unprimeable number, because it can be changed into a prime (21691464521) 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, 4618758 + ... + 4623451.

It is an arithmetic number, because the mean of its divisors is an integer number (5425177270).

Almost surely, 2^21691464523 is an apocalyptic number.

21691464523 is a deficient number, since it is larger than the sum of its proper divisors (9244557).

21691464523 is an equidigital number, since it uses as much as digits as its factorization.

21691464523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9244556.

The product of its digits is 311040, while the sum is 43.

The spelling of 21691464523 in words is "twenty-one billion, six hundred ninety-one million, four hundred sixty-four thousand, five hundred twenty-three".