21615646564406 has 8 divisors (see below), whose sum is σ = 32538855861144. Its totient is φ = 10769361277360.

The previous prime is 21615646564397. The next prime is 21615646564409. The reversal of 21615646564406 is 60446564651612.

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

It is a super-2 number, since 2×21615646564406² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21615646564409) 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, 19231001720 + ... + 19231002843.

It is an arithmetic number, because the mean of its divisors is an integer number (4067356982643).

Almost surely, 2^{21615646564406} is an apocalyptic number.

21615646564406 is a deficient number, since it is larger than the sum of its proper divisors (10923209296738).

21615646564406 is a wasteful number, since it uses less digits than its factorization.

21615646564406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38462004846.

The product of its (nonzero) digits is 24883200, while the sum is 56.

The spelling of 21615646564406 in words is "twenty-one trillion, six hundred fifteen billion, six hundred forty-six million, five hundred sixty-four thousand, four hundred six".