2178220821 has 32 divisors (see below), whose sum is σ = 3413360640. Its totient is φ = 1209473856.

The previous prime is 2178220787. The next prime is 2178220831. The reversal of 2178220821 is 1280228712.

It is not a de Polignac number, because 2178220821 - 2¹¹ = 2178218773 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2178220831) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 843310 + ... + 845888.

It is an arithmetic number, because the mean of its divisors is an integer number (106667520).

Almost surely, 2^2178220821 is an apocalyptic number.

2178220821 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2178220821 is a deficient number, since it is larger than the sum of its proper divisors (1235139819).

2178220821 is a wasteful number, since it uses less digits than its factorization.

2178220821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3713.

The product of its (nonzero) digits is 7168, while the sum is 33.

The square root of 2178220821 is about 46671.4133169331. The cubic root of 2178220821 is about 1296.2854160814.

The spelling of 2178220821 in words is "two billion, one hundred seventy-eight million, two hundred twenty thousand, eight hundred twenty-one".