81401780 has 24 divisors (see below), whose sum is σ = 181000008. Its totient is φ = 30645248.

The previous prime is 81401777. The next prime is 81401783. The reversal of 81401780 is 8710418.

It is an interprime number because it is at equal distance from previous prime (81401777) and next prime (81401783).

It can be written as a sum of positive squares in 4 ways, for example, as 20124196 + 61277584 = 4486^2 + 7828^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81401783) 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, 119369 + ... + 120048.

It is an arithmetic number, because the mean of its divisors is an integer number (7541667).

Almost surely, 2^81401780 is an apocalyptic number.

It is an amenable number.

81401780 is an abundant number, since it is smaller than the sum of its proper divisors (99598228).

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

81401780 is a wasteful number, since it uses less digits than its factorization.

81401780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 239443 (or 239441 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 81401780 is about 9022.2934999921. The cubic root of 81401780 is about 433.3890828997.

The spelling of 81401780 in words is "eighty-one million, four hundred one thousand, seven hundred eighty".