81000551 has 4 divisors (see below), whose sum is σ = 83613504. Its totient is φ = 78387600.

The previous prime is 81000541. The next prime is 81000571. The reversal of 81000551 is 15500018.

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 81000551 - 2⁶ = 81000487 is a prime.

It is a super-2 number, since 2×81000551² = 13122178524607202, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81000541) 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, 1306430 + ... + 1306491.

It is an arithmetic number, because the mean of its divisors is an integer number (20903376).

Almost surely, 2^81000551 is an apocalyptic number.

81000551 is a deficient number, since it is larger than the sum of its proper divisors (2612953).

81000551 is a wasteful number, since it uses less digits than its factorization.

81000551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2612952.

The product of its (nonzero) digits is 200, while the sum is 20.

The square root of 81000551 is about 9000.0306110591. The cubic root of 81000551 is about 432.6758521758.

Adding to 81000551 its reverse (15500018), we get a palindrome (96500569).

The spelling of 81000551 in words is "eighty-one million, five hundred fifty-one", and thus it is an aban number.