21394117861 has 4 divisors (see below), whose sum is σ = 21400003852. Its totient is φ = 21388231872.

The previous prime is 21394117783. The next prime is 21394117903. The reversal of 21394117861 is 16871149312.

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 7277113636 + 14117004225 = 85306^2 + 118815^2 .

It is a cyclic number.

It is not a de Polignac number, because 21394117861 - 2¹⁵ = 21394085093 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 (21394127861) 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, 2937540 + ... + 2944813.

It is an arithmetic number, because the mean of its divisors is an integer number (5350000963).

Almost surely, 2^21394117861 is an apocalyptic number.

It is an amenable number.

21394117861 is a deficient number, since it is larger than the sum of its proper divisors (5885991).

21394117861 is an equidigital number, since it uses as much as digits as its factorization.

21394117861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5885990.

The product of its digits is 72576, while the sum is 43.

The spelling of 21394117861 in words is "twenty-one billion, three hundred ninety-four million, one hundred seventeen thousand, eight hundred sixty-one".