217920406447 has 4 divisors (see below), whose sum is σ = 222988322920. Its totient is φ = 212852489976.

The previous prime is 217920406423. The next prime is 217920406469. The reversal of 217920406447 is 744604029712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217920406447 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 217920406397 and 217920406406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217920406147) 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, 2533958172 + ... + 2533958257.

It is an arithmetic number, because the mean of its divisors is an integer number (55747080730).

Almost surely, 2^217920406447 is an apocalyptic number.

217920406447 is a deficient number, since it is larger than the sum of its proper divisors (5067916473).

217920406447 is an equidigital number, since it uses as much as digits as its factorization.

217920406447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5067916472.

The product of its (nonzero) digits is 677376, while the sum is 46.

The spelling of 217920406447 in words is "two hundred seventeen billion, nine hundred twenty million, four hundred six thousand, four hundred forty-seven".