81906420 has 24 divisors (see below), whose sum is σ = 229338144. Its totient is φ = 21841696.

The previous prime is 81906413. The next prime is 81906439. The reversal of 81906420 is 2460918.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 682494 + ... + 682613.

It is an arithmetic number, because the mean of its divisors is an integer number (9555756).

Almost surely, 2^81906420 is an apocalyptic number.

It is an amenable number.

81906420 is an abundant number, since it is smaller than the sum of its proper divisors (147431724).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81906420 is a wasteful number, since it uses less digits than its factorization.

81906420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1365119 (or 1365117 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 81906420 is about 9050.2165719943. The cubic root of 81906420 is about 434.2828187670.

The spelling of 81906420 in words is "eighty-one million, nine hundred six thousand, four hundred twenty".