81903421 has 2 divisors, whose sum is σ = 81903422. Its totient is φ = 81903420.

The previous prime is 81903389. The next prime is 81903431. The reversal of 81903421 is 12430918.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74822500 + 7080921 = 8650^2 + 2661^2 .

It is a cyclic number.

It is not a de Polignac number, because 81903421 - 2⁵ = 81903389 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81903421.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81903431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40951710 + 40951711.

It is an arithmetic number, because the mean of its divisors is an integer number (40951711).

Almost surely, 2^81903421 is an apocalyptic number.

It is an amenable number.

81903421 is a deficient number, since it is larger than the sum of its proper divisors (1).

81903421 is an equidigital number, since it uses as much as digits as its factorization.

81903421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 81903421 is about 9050.0508838349. The cubic root of 81903421 is about 434.2775182868.

It can be divided in two parts, 8190 and 3421, that added together give a palindrome (11611).

The spelling of 81903421 in words is "eighty-one million, nine hundred three thousand, four hundred twenty-one".