2166342821 has 4 divisors (see below), whose sum is σ = 2166436512. Its totient is φ = 2166249132.

The previous prime is 2166342781. The next prime is 2166342823. The reversal of 2166342821 is 1282436612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 2166342821 - 2⁶ = 2166342757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2166342823) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15470 + ... + 67616.

It is an arithmetic number, because the mean of its divisors is an integer number (541609128).

Almost surely, 2^2166342821 is an apocalyptic number.

It is an amenable number.

2166342821 is a deficient number, since it is larger than the sum of its proper divisors (93691).

2166342821 is an equidigital number, since it uses as much as digits as its factorization.

2166342821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93690.

The product of its digits is 27648, while the sum is 35.

The square root of 2166342821 is about 46543.9880220851. The cubic root of 2166342821 is about 1293.9248732290.

The spelling of 2166342821 in words is "two billion, one hundred sixty-six million, three hundred forty-two thousand, eight hundred twenty-one".