2181291021 has 24 divisors (see below), whose sum is σ = 3877852160. Its totient is φ = 1150570656.

The previous prime is 2181291001. The next prime is 2181291023. The reversal of 2181291021 is 1201921812.

It is not a de Polignac number, because 2181291021 - 2⁵ = 2181290989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181291023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1330861 + ... + 1332498.

Almost surely, 2^2181291021 is an apocalyptic number.

2181291021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

2181291021 is a deficient number, since it is larger than the sum of its proper divisors (1696561139).

2181291021 is a wasteful number, since it uses less digits than its factorization.

2181291021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2663385 (or 2663382 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 27.

The square root of 2181291021 is about 46704.2933893662. The cubic root of 2181291021 is about 1296.8941678115.

The spelling of 2181291021 in words is "two billion, one hundred eighty-one million, two hundred ninety-one thousand, twenty-one".