21621206505215 has 16 divisors (see below), whose sum is σ = 26055729648000. Its totient is φ = 17223453553152.

The previous prime is 21621206505193. The next prime is 21621206505229. The reversal of 21621206505215 is 51250560212612.

It is a cyclic number.

It is not a de Polignac number, because 21621206505215 - 2⁴⁴ = 4029020460799 is a prime.

It is a congruent number.

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, 17708261 + ... + 18889809.

It is an arithmetic number, because the mean of its divisors is an integer number (1628483103000).

Almost surely, 2^{21621206505215} is an apocalyptic number.

21621206505215 is a deficient number, since it is larger than the sum of its proper divisors (4434523142785).

21621206505215 is a wasteful number, since it uses less digits than its factorization.

21621206505215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1197106.

The product of its (nonzero) digits is 72000, while the sum is 38.

Adding to 21621206505215 its reverse (51250560212612), we get a palindrome (72871766717827).

The spelling of 21621206505215 in words is "twenty-one trillion, six hundred twenty-one billion, two hundred six million, five hundred five thousand, two hundred fifteen".