172898787721 has 27 divisors (see below), whose sum is σ = 192433130253. Its totient is φ = 155230562520.

The previous prime is 172898787689. The next prime is 172898787751. The reversal of 172898787721 is 127787898271.

The square root of 172898787721 is 415811.

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

It is not a de Polignac number, because 172898787721 - 2⁵ = 172898787689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (172898787751) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 471113680 + ... + 471114046.

Almost surely, 2^172898787721 is an apocalyptic number.

172898787721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

172898787721 is the 415811-st square number.

172898787721 is the 207906-th centered octagonal number.

It is an amenable number.

172898787721 is a deficient number, since it is larger than the sum of its proper divisors (19534342532).

172898787721 is an frugal number, since it uses more digits than its factorization.

172898787721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 962 (or 481 counting only the distinct ones).

The product of its digits is 44255232, while the sum is 67.

The spelling of 172898787721 in words is "one hundred seventy-two billion, eight hundred ninety-eight million, seven hundred eighty-seven thousand, seven hundred twenty-one".