21687950205 has 32 divisors (see below), whose sum is σ = 39453025920. Its totient is φ = 11297905920.

The previous prime is 21687950201. The next prime is 21687950213. The reversal of 21687950205 is 50205978612.

It is not a de Polignac number, because 21687950205 - 2² = 21687950201 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21687950201) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1862236 + ... + 1873845.

It is an arithmetic number, because the mean of its divisors is an integer number (1232907060).

Almost surely, 2^21687950205 is an apocalyptic number.

It is an amenable number.

21687950205 is a deficient number, since it is larger than the sum of its proper divisors (17765075715).

21687950205 is a wasteful number, since it uses less digits than its factorization.

21687950205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3736138 (or 3736132 counting only the distinct ones).

The product of its (nonzero) digits is 302400, while the sum is 45.

The spelling of 21687950205 in words is "twenty-one billion, six hundred eighty-seven million, nine hundred fifty thousand, two hundred five".