81863553 has 4 divisors (see below), whose sum is σ = 109151408. Its totient is φ = 54575700.

The previous prime is 81863543. The next prime is 81863563. The reversal of 81863553 is 35536818.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (81863543) and next prime (81863563).

It is not a de Polignac number, because 81863553 - 2⁵ = 81863521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81863543) 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, 13643923 + ... + 13643928.

It is an arithmetic number, because the mean of its divisors is an integer number (27287852).

Almost surely, 2^81863553 is an apocalyptic number.

It is an amenable number.

81863553 is a deficient number, since it is larger than the sum of its proper divisors (27287855).

81863553 is a wasteful number, since it uses less digits than its factorization.

81863553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27287854.

The product of its digits is 86400, while the sum is 39.

The square root of 81863553 is about 9047.8479761764. The cubic root of 81863553 is about 434.2070426546.

The spelling of 81863553 in words is "eighty-one million, eight hundred sixty-three thousand, five hundred fifty-three".