81642420 has 36 divisors (see below), whose sum is σ = 247649220. Its totient is φ = 21771264.

The previous prime is 81642413. The next prime is 81642427. The reversal of 81642420 is 2424618.

It is an interprime number because it is at equal distance from previous prime (81642413) and next prime (81642427).

It can be written as a sum of positive squares in 2 ways, for example, as 34363044 + 47279376 = 5862^2 + 6876^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81642427) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 226605 + ... + 226964.

It is an arithmetic number, because the mean of its divisors is an integer number (6879145).

Almost surely, 2^81642420 is an apocalyptic number.

It is an amenable number.

81642420 is an abundant number, since it is smaller than the sum of its proper divisors (166006800).

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

81642420 is a wasteful number, since it uses less digits than its factorization.

81642420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 453584 (or 453579 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 27.

The square root of 81642420 is about 9035.6195139016. The cubic root of 81642420 is about 433.8157244679.

The spelling of 81642420 in words is "eighty-one million, six hundred forty-two thousand, four hundred twenty".