81921403 has 16 divisors (see below), whose sum is σ = 86228352. Its totient is φ = 77760000.

The previous prime is 81921401. The next prime is 81921421. The reversal of 81921403 is 30412918.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 81921403 - 2¹ = 81921401 is a prime.

It is a super-2 number, since 2×81921403² = 13422232538976818, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81921401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 302158 + ... + 302428.

It is an arithmetic number, because the mean of its divisors is an integer number (5389272).

Almost surely, 2^81921403 is an apocalyptic number.

81921403 is a deficient number, since it is larger than the sum of its proper divisors (4306949).

81921403 is a wasteful number, since it uses less digits than its factorization.

81921403 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 486.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 81921403 is about 9051.0443043883. The cubic root of 81921403 is about 434.3092980212.

It can be divided in two parts, 819 and 21403, that added together give a palindrome (22222).

The spelling of 81921403 in words is "eighty-one million, nine hundred twenty-one thousand, four hundred three".