81289021 has 8 divisors (see below), whose sum is σ = 88792704. Its totient is φ = 73804320.

The previous prime is 81289003. The next prime is 81289063. The reversal of 81289021 is 12098218.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81289021 - 2¹¹ = 81286973 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81286021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5116 + ... + 13738.

It is an arithmetic number, because the mean of its divisors is an integer number (11099088).

Almost surely, 2^81289021 is an apocalyptic number.

It is an amenable number.

81289021 is a deficient number, since it is larger than the sum of its proper divisors (7503683).

81289021 is a wasteful number, since it uses less digits than its factorization.

81289021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9491.

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 81289021 is about 9016.0424244787. The cubic root of 81289021 is about 433.1888780170.

The spelling of 81289021 in words is "eighty-one million, two hundred eighty-nine thousand, twenty-one".