172643721 has 16 divisors (see below), whose sum is σ = 245602368. Its totient is φ = 107494400.

The previous prime is 172643719. The next prime is 172643729. The reversal of 172643721 is 127346271.

It is not a de Polignac number, because 172643721 - 2¹ = 172643719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (172643729) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6240 + ... + 19601.

It is an arithmetic number, because the mean of its divisors is an integer number (15350148).

Almost surely, 2^172643721 is an apocalyptic number.

It is an amenable number.

172643721 is a deficient number, since it is larger than the sum of its proper divisors (72958647).

172643721 is a wasteful number, since it uses less digits than its factorization.

172643721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25992.

The product of its digits is 14112, while the sum is 33.

The square root of 172643721 is about 13139.3957623629. The cubic root of 172643721 is about 556.8226966890.

Adding to 172643721 its reverse (127346271), we get a palindrome (299989992).

The spelling of 172643721 in words is "one hundred seventy-two million, six hundred forty-three thousand, seven hundred twenty-one".