21388402117 has 4 divisors (see below), whose sum is σ = 22646543436. Its totient is φ = 20130260800.

The previous prime is 21388402111. The next prime is 21388402129. The reversal of 21388402117 is 71120488312.

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 17255712321 + 4132689796 = 131361^2 + 64286^2 .

It is a cyclic number.

It is not a de Polignac number, because 21388402117 - 2³ = 21388402109 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 (21388402111) 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, 629070634 + ... + 629070667.

It is an arithmetic number, because the mean of its divisors is an integer number (5661635859).

Almost surely, 2^21388402117 is an apocalyptic number.

It is an amenable number.

21388402117 is a deficient number, since it is larger than the sum of its proper divisors (1258141319).

21388402117 is a wasteful number, since it uses less digits than its factorization.

21388402117 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1258141318.

The product of its (nonzero) digits is 21504, while the sum is 37.

The spelling of 21388402117 in words is "twenty-one billion, three hundred eighty-eight million, four hundred two thousand, one hundred seventeen".