81021040 has 20 divisors (see below), whose sum is σ = 188374104. Its totient is φ = 32408384.

The previous prime is 81021037. The next prime is 81021097. The reversal of 81021040 is 4012018.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 506302 + ... + 506461.

Almost surely, 2^81021040 is an apocalyptic number.

81021040 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81021040 is an abundant number, since it is smaller than the sum of its proper divisors (107353064).

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

81021040 is a wasteful number, since it uses less digits than its factorization.

81021040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1012776 (or 1012770 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

The square root of 81021040 is about 9001.1688129931. The cubic root of 81021040 is about 432.7123307267.

Adding to 81021040 its reverse (4012018), we get a palindrome (85033058).

The spelling of 81021040 in words is "eighty-one million, twenty-one thousand, forty".