2172820638 has 16 divisors (see below), whose sum is σ = 4387833216. Its totient is φ = 717241560.

The previous prime is 2172820633. The next prime is 2172820651. The reversal of 2172820638 is 8360282712.

It is a super-3 number, since 3×2172820638³ (a number of 29 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 2172820596 and 2172820605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2172820633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1757328 + ... + 1758563.

It is an arithmetic number, because the mean of its divisors is an integer number (274239576).

Almost surely, 2^2172820638 is an apocalyptic number.

2172820638 is an abundant number, since it is smaller than the sum of its proper divisors (2215012578).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

2172820638 is a wasteful number, since it uses less digits than its factorization.

2172820638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3515999.

The product of its (nonzero) digits is 64512, while the sum is 39.

The square root of 2172820638 is about 46613.5241963102. The cubic root of 2172820638 is about 1295.2132916422.

The spelling of 2172820638 in words is "two billion, one hundred seventy-two million, eight hundred twenty thousand, six hundred thirty-eight".