21516666225 has 12 divisors (see below), whose sum is σ = 35574221616. Its totient is φ = 11475555280.

The previous prime is 21516666211. The next prime is 21516666247. The reversal of 21516666225 is 52266661512.

It is a happy number.

It is not a de Polignac number, because 21516666225 - 2⁴ = 21516666209 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 143444367 + ... + 143444516.

It is an arithmetic number, because the mean of its divisors is an integer number (2964518468).

Almost surely, 2^21516666225 is an apocalyptic number.

21516666225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21516666225 is a deficient number, since it is larger than the sum of its proper divisors (14057555391).

21516666225 is a wasteful number, since it uses less digits than its factorization.

21516666225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286888896 (or 286888891 counting only the distinct ones).

The product of its digits is 259200, while the sum is 42.

The spelling of 21516666225 in words is "twenty-one billion, five hundred sixteen million, six hundred sixty-six thousand, two hundred twenty-five".