21154124405 has 4 divisors (see below), whose sum is σ = 25384949292. Its totient is φ = 16923299520.

The previous prime is 21154124377. The next prime is 21154124491. The reversal of 21154124405 is 50442145112.

It is a happy number.

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 10631878321 + 10522246084 = 103111^2 + 102578^2 .

It is not a de Polignac number, because 21154124405 - 2¹⁰ = 21154123381 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2115412436 + ... + 2115412445.

It is an arithmetic number, because the mean of its divisors is an integer number (6346237323).

Almost surely, 2^21154124405 is an apocalyptic number.

It is an amenable number.

21154124405 is a deficient number, since it is larger than the sum of its proper divisors (4230824887).

21154124405 is an equidigital number, since it uses as much as digits as its factorization.

21154124405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4230824886.

The product of its (nonzero) digits is 6400, while the sum is 29.

Adding to 21154124405 its reverse (50442145112), we get a palindrome (71596269517).

The spelling of 21154124405 in words is "twenty-one billion, one hundred fifty-four million, one hundred twenty-four thousand, four hundred five".