81353021 has 4 divisors (see below), whose sum is σ = 83977344. Its totient is φ = 78728700.

The previous prime is 81353011. The next prime is 81353023. The reversal of 81353021 is 12035318.

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 a cyclic number.

It is not a de Polignac number, because 81353021 - 2¹⁰ = 81351997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81353023) 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, 1312115 + ... + 1312176.

It is an arithmetic number, because the mean of its divisors is an integer number (20994336).

Almost surely, 2^81353021 is an apocalyptic number.

It is an amenable number.

81353021 is a deficient number, since it is larger than the sum of its proper divisors (2624323).

81353021 is a wasteful number, since it uses less digits than its factorization.

81353021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2624322.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 81353021 is about 9019.5909552485. The cubic root of 81353021 is about 433.3025334453.

Adding to 81353021 its reverse (12035318), we get a palindrome (93388339).

The spelling of 81353021 in words is "eighty-one million, three hundred fifty-three thousand, twenty-one".