221665943402500 has 135 divisors (see below), whose sum is σ = 487603039854931. Its totient is φ = 88145579380000.

The previous prime is 221665943402483. The next prime is 221665943402509. The reversal of 221665943402500 is 5204349566122.

The square root of 221665943402500 is 14888450.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 2 ways, for example, as 17378609962756 + 204287333439744 = 4168766^2 + 14292912^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221665943402509) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 142184696721 + ... + 142184698279.

Almost surely, 2^{221665943402500} is an apocalyptic number.

221665943402500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

221665943402500 is the 14888450-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221665943402500

221665943402500 is an abundant number, since it is smaller than the sum of its proper divisors (265937096452431).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

221665943402500 is an frugal number, since it uses more digits than its factorization.

221665943402500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3524 (or 1757 counting only the distinct ones).

The product of its (nonzero) digits is 3110400, while the sum is 49.

The spelling of 221665943402500 in words is "two hundred twenty-one trillion, six hundred sixty-five billion, nine hundred forty-three million, four hundred two thousand, five hundred".