172211821 has 2 divisors, whose sum is σ = 172211822. Its totient is φ = 172211820.

The previous prime is 172211813. The next prime is 172211827. The reversal of 172211821 is 128112271.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 117288900 + 54922921 = 10830^2 + 7411^2 .

It is a cyclic number.

It is not a de Polignac number, because 172211821 - 2³ = 172211813 is a prime.

It is a super-2 number, since 2×172211821² = 59313822584272082, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (172211827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 86105910 + 86105911.

It is an arithmetic number, because the mean of its divisors is an integer number (86105911).

Almost surely, 2^172211821 is an apocalyptic number.

It is an amenable number.

172211821 is a deficient number, since it is larger than the sum of its proper divisors (1).

172211821 is an equidigital number, since it uses as much as digits as its factorization.

172211821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 448, while the sum is 25.

The square root of 172211821 is about 13122.9501637399. The cubic root of 172211821 is about 556.3579775066.

The spelling of 172211821 in words is "one hundred seventy-two million, two hundred eleven thousand, eight hundred twenty-one".