20090640 has 80 divisors (see below), whose sum is σ = 62995968. Its totient is φ = 5296128.

The previous prime is 20090627. The next prime is 20090647. The reversal of 20090640 is 4609002.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (20090647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22849 + ... + 23711.

Almost surely, 2^20090640 is an apocalyptic number.

20090640 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 20090640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31497984).

20090640 is an abundant number, since it is smaller than the sum of its proper divisors (42905328).

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

20090640 is a wasteful number, since it uses less digits than its factorization.

20090640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 976 (or 970 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 21.

The square root of 20090640 is about 4482.2583593541. The cubic root of 20090640 is about 271.8512017748.

Adding to 20090640 its reverse (4609002), we get a palindrome (24699642).

The spelling of 20090640 in words is "twenty million, ninety thousand, six hundred forty".