172977991 has 4 divisors (see below), whose sum is σ = 173695984. Its totient is φ = 172260000.

The previous prime is 172977989. The next prime is 172978007. The reversal of 172977991 is 199779271.

172977991 = T₂₉₈ + T₂₉₉ + ... + T₁₀₂₀.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199779271 = 263 ⋅759617.

It is a cyclic number.

It is not a de Polignac number, because 172977991 - 2¹ = 172977989 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 (172977901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 358635 + ... + 359116.

It is an arithmetic number, because the mean of its divisors is an integer number (43423996).

Almost surely, 2^172977991 is an apocalyptic number.

172977991 is a deficient number, since it is larger than the sum of its proper divisors (717993).

172977991 is an equidigital number, since it uses as much as digits as its factorization.

172977991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 717992.

The product of its digits is 500094, while the sum is 52.

The square root of 172977991 is about 13152.1097547124. The cubic root of 172977991 is about 557.1818353901.

The spelling of 172977991 in words is "one hundred seventy-two million, nine hundred seventy-seven thousand, nine hundred ninety-one".