21605123023751 has 4 divisors (see below), whose sum is σ = 21605232913104. Its totient is φ = 21605013134400.

The previous prime is 21605123023747. The next prime is 21605123023823. The reversal of 21605123023751 is 15732032150612.

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 21605123023751 - 2² = 21605123023747 is a prime.

It is a super-2 number, since 2×21605123023751² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605123023651) 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, 54649235 + ... + 55043156.

It is an arithmetic number, because the mean of its divisors is an integer number (5401308228276).

Almost surely, 2^{21605123023751} is an apocalyptic number.

21605123023751 is a deficient number, since it is larger than the sum of its proper divisors (109889353).

21605123023751 is a wasteful number, since it uses less digits than its factorization.

21605123023751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109889352.

The product of its (nonzero) digits is 75600, while the sum is 38.

The spelling of 21605123023751 in words is "twenty-one trillion, six hundred five billion, one hundred twenty-three million, twenty-three thousand, seven hundred fifty-one".