21404434551 has 4 divisors (see below), whose sum is σ = 28539246072. Its totient is φ = 14269623032.

The previous prime is 21404434537. The next prime is 21404434603. The reversal of 21404434551 is 15543440412.

It is a happy number.

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 21404434551 - 2¹¹ = 21404432503 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21404434351) 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, 3567405756 + ... + 3567405761.

It is an arithmetic number, because the mean of its divisors is an integer number (7134811518).

Almost surely, 2^21404434551 is an apocalyptic number.

21404434551 is a deficient number, since it is larger than the sum of its proper divisors (7134811521).

21404434551 is an equidigital number, since it uses as much as digits as its factorization.

21404434551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7134811520.

The product of its (nonzero) digits is 38400, while the sum is 33.

Adding to 21404434551 its reverse (15543440412), we get a palindrome (36947874963).

The spelling of 21404434551 in words is "twenty-one billion, four hundred four million, four hundred thirty-four thousand, five hundred fifty-one".