81798021 has 12 divisors (see below), whose sum is σ = 124371520. Its totient is φ = 51661800.

The previous prime is 81798019. The next prime is 81798029. The reversal of 81798021 is 12089718.

It is not a de Polignac number, because 81798021 - 2¹ = 81798019 is a prime.

It is a Duffinian number.

It is a plaindrome in base 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81798029) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 239005 + ... + 239346.

Almost surely, 2^81798021 is an apocalyptic number.

It is an amenable number.

81798021 is a deficient number, since it is larger than the sum of its proper divisors (42573499).

81798021 is a wasteful number, since it uses less digits than its factorization.

81798021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 478376 (or 478373 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 81798021 is about 9044.2258375164. The cubic root of 81798021 is about 434.0911504132.

The spelling of 81798021 in words is "eighty-one million, seven hundred ninety-eight thousand, twenty-one".