2172985861 has 2 divisors, whose sum is σ = 2172985862. Its totient is φ = 2172985860.

The previous prime is 2172985823. The next prime is 2172985877. The reversal of 2172985861 is 1685892712.

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., 1208883361 + 964102500 = 34769^2 + 31050^2 .

It is a cyclic number.

It is not a de Polignac number, because 2172985861 - 2¹³ = 2172977669 is a prime.

It is a super-2 number, since 2×2172985861² = 9443735104211822642, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2172985891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1086492930 + 1086492931.

It is an arithmetic number, because the mean of its divisors is an integer number (1086492931).

Almost surely, 2^2172985861 is an apocalyptic number.

It is an amenable number.

2172985861 is a deficient number, since it is larger than the sum of its proper divisors (1).

2172985861 is an equidigital number, since it uses as much as digits as its factorization.

2172985861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 483840, while the sum is 49.

The square root of 2172985861 is about 46615.2964272459. The cubic root of 2172985861 is about 1295.2461204912.

The spelling of 2172985861 in words is "two billion, one hundred seventy-two million, nine hundred eighty-five thousand, eight hundred sixty-one".