21019236709 has 4 divisors (see below), whose sum is σ = 21050285004. Its totient is φ = 20988188416.

The previous prime is 21019236697. The next prime is 21019236739. The reversal of 21019236709 is 90763291012.

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

It can be written as a sum of positive squares in 2 ways, for example, as 20912052100 + 107184609 = 144610^2 + 10353^2 .

It is a cyclic number.

It is not a de Polignac number, because 21019236709 - 2⁹ = 21019236197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21019236739) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15523132 + ... + 15524485.

It is an arithmetic number, because the mean of its divisors is an integer number (5262571251).

Almost surely, 2^21019236709 is an apocalyptic number.

It is an amenable number.

21019236709 is a deficient number, since it is larger than the sum of its proper divisors (31048295).

21019236709 is an equidigital number, since it uses as much as digits as its factorization.

21019236709 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31048294.

The product of its (nonzero) digits is 40824, while the sum is 40.

The spelling of 21019236709 in words is "twenty-one billion, nineteen million, two hundred thirty-six thousand, seven hundred nine".