221656715551 has 4 divisors (see below), whose sum is σ = 229300050600. Its totient is φ = 214013380504.

The previous prime is 221656715549. The next prime is 221656715573. The reversal of 221656715551 is 155517656122.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 155517656122 = 2 ⋅77758828061.

It is a cyclic number.

It is not a de Polignac number, because 221656715551 - 2¹ = 221656715549 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221656715521) 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, 3821667481 + ... + 3821667538.

It is an arithmetic number, because the mean of its divisors is an integer number (57325012650).

Almost surely, 2^221656715551 is an apocalyptic number.

221656715551 is a deficient number, since it is larger than the sum of its proper divisors (7643335049).

221656715551 is an equidigital number, since it uses as much as digits as its factorization.

221656715551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7643335048.

The product of its digits is 630000, while the sum is 46.

The spelling of 221656715551 in words is "two hundred twenty-one billion, six hundred fifty-six million, seven hundred fifteen thousand, five hundred fifty-one".