197217721 has 4 divisors (see below), whose sum is σ = 197860432. Its totient is φ = 196575012.

The previous prime is 197217689. The next prime is 197217743. The reversal of 197217721 is 127712791.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 127712791 = 2141 ⋅59651.

It is a cyclic number.

It is not a de Polignac number, because 197217721 - 2⁵ = 197217689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (197217791) 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, 320895 + ... + 321508.

It is an arithmetic number, because the mean of its divisors is an integer number (49465108).

Almost surely, 2^197217721 is an apocalyptic number.

It is an amenable number.

197217721 is a deficient number, since it is larger than the sum of its proper divisors (642711).

197217721 is an equidigital number, since it uses as much as digits as its factorization.

197217721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 642710.

The product of its digits is 12348, while the sum is 37.

The square root of 197217721 is about 14043.4226953403. The cubic root of 197217721 is about 582.0790634708.

The spelling of 197217721 in words is "one hundred ninety-seven million, two hundred seventeen thousand, seven hundred twenty-one".