21005221715 has 16 divisors (see below), whose sum is σ = 27250021920. Its totient is φ = 15489480960.

The previous prime is 21005221663. The next prime is 21005221751. The reversal of 21005221715 is 51712250012.

It is not a de Polignac number, because 21005221715 - 2³² = 16710254419 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2984426 + ... + 2991455.

It is an arithmetic number, because the mean of its divisors is an integer number (1703126370).

Almost surely, 2^21005221715 is an apocalyptic number.

21005221715 is a deficient number, since it is larger than the sum of its proper divisors (6244800205).

21005221715 is a wasteful number, since it uses less digits than its factorization.

21005221715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5975942.

The product of its (nonzero) digits is 1400, while the sum is 26.

Adding to 21005221715 its reverse (51712250012), we get a palindrome (72717471727).

The spelling of 21005221715 in words is "twenty-one billion, five million, two hundred twenty-one thousand, seven hundred fifteen".