81005229491 has 4 divisors (see below), whose sum is σ = 81006144432. Its totient is φ = 81004314552.

The previous prime is 81005229467. The next prime is 81005229497. The reversal of 81005229491 is 19492250018.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81005229491 - 2²² = 81001035187 is a prime.

It is a super-2 number, since 2×81005229491² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81005229497) 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, 308495 + ... + 507128.

It is an arithmetic number, because the mean of its divisors is an integer number (20251536108).

Almost surely, 2^81005229491 is an apocalyptic number.

81005229491 is a deficient number, since it is larger than the sum of its proper divisors (914941).

81005229491 is an equidigital number, since it uses as much as digits as its factorization.

81005229491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 914940.

The product of its (nonzero) digits is 51840, while the sum is 41.

The spelling of 81005229491 in words is "eighty-one billion, five million, two hundred twenty-nine thousand, four hundred ninety-one".