20042640 has 120 divisors (see below), whose sum is σ = 69870528. Its totient is φ = 5339520.

The previous prime is 20042621. The next prime is 20042653. The reversal of 20042640 is 4624002.

20042640 is a `hidden beast` number, since 20 + 0 + 4 + 2 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18925 + ... + 19955.

Almost surely, 2^20042640 is an apocalyptic number.

20042640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20042640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34935264).

20042640 is an abundant number, since it is smaller than the sum of its proper divisors (49827888).

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

20042640 is a wasteful number, since it uses less digits than its factorization.

20042640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1059 (or 1041 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 18.

The square root of 20042640 is about 4476.9007136634. The cubic root of 20042640 is about 271.6345293427.

Adding to 20042640 its reverse (4624002), we get a palindrome (24666642).

The spelling of 20042640 in words is "twenty million, forty-two thousand, six hundred forty".