21436517021 has 4 divisors (see below), whose sum is σ = 21447307392. Its totient is φ = 21425726652.

The previous prime is 21436516973. The next prime is 21436517059. The reversal of 21436517021 is 12071563412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21436517021 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 (21436517521) 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, 5392205 + ... + 5396178.

It is an arithmetic number, because the mean of its divisors is an integer number (5361826848).

Almost surely, 2^21436517021 is an apocalyptic number.

It is an amenable number.

21436517021 is a deficient number, since it is larger than the sum of its proper divisors (10790371).

21436517021 is a wasteful number, since it uses less digits than its factorization.

21436517021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10790370.

The product of its (nonzero) digits is 10080, while the sum is 32.

The spelling of 21436517021 in words is "twenty-one billion, four hundred thirty-six million, five hundred seventeen thousand, twenty-one".