21387155309 has 8 divisors (see below), whose sum is σ = 23034886560. Its totient is φ = 19739790576.

The previous prime is 21387155297. The next prime is 21387155311. The reversal of 21387155309 is 90355178312.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21387155309 is a prime.

It is a super-2 number, since 2×21387155309² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21387155309.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387155359) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36182 + ... + 209960.

It is an arithmetic number, because the mean of its divisors is an integer number (2879360820).

Almost surely, 2^21387155309 is an apocalyptic number.

It is an amenable number.

21387155309 is a deficient number, since it is larger than the sum of its proper divisors (1647731251).

21387155309 is a wasteful number, since it uses less digits than its factorization.

21387155309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183259.

The product of its (nonzero) digits is 226800, while the sum is 44.

The spelling of 21387155309 in words is "twenty-one billion, three hundred eighty-seven million, one hundred fifty-five thousand, three hundred nine".