2161997421 has 16 divisors (see below), whose sum is σ = 2896974720. Its totient is φ = 1434191360.

The previous prime is 2161997399. The next prime is 2161997437. The reversal of 2161997421 is 1247991612.

It is a cyclic number.

It is not a de Polignac number, because 2161997421 - 2⁷ = 2161997293 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2161997471) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 827365 + ... + 829973.

It is an arithmetic number, because the mean of its divisors is an integer number (181060920).

Almost surely, 2^2161997421 is an apocalyptic number.

It is an amenable number.

2161997421 is a deficient number, since it is larger than the sum of its proper divisors (734977299).

2161997421 is a wasteful number, since it uses less digits than its factorization.

2161997421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3876.

The product of its digits is 54432, while the sum is 42.

The square root of 2161997421 is about 46497.2840174563. The cubic root of 2161997421 is about 1293.0591461769.

The spelling of 2161997421 in words is "two billion, one hundred sixty-one million, nine hundred ninety-seven thousand, four hundred twenty-one".