21756136405 has 8 divisors (see below), whose sum is σ = 26108822232. Its totient is φ = 17403936768.

The previous prime is 21756136397. The next prime is 21756136417. The reversal of 21756136405 is 50463165712.

It can be written as a sum of positive squares in 4 ways, for example, as 892933924 + 20863202481 = 29882^2 + 144441^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21756136405 - 2³ = 21756136397 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 7 ways as a sum of consecutive naturals, for example, 14532 + ... + 209101.

It is an arithmetic number, because the mean of its divisors is an integer number (3263602779).

Almost surely, 2^21756136405 is an apocalyptic number.

It is an amenable number.

21756136405 is a deficient number, since it is larger than the sum of its proper divisors (4352685827).

21756136405 is a wasteful number, since it uses less digits than its factorization.

21756136405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243095.

The product of its (nonzero) digits is 151200, while the sum is 40.

The spelling of 21756136405 in words is "twenty-one billion, seven hundred fifty-six million, one hundred thirty-six thousand, four hundred five".