20669640 has 64 divisors (see below), whose sum is σ = 64713600. Its totient is φ = 5271552.

The previous prime is 20669611. The next prime is 20669641. The reversal of 20669640 is 4696602.

It is not an unprimeable number, because it can be changed into a prime (20669641) 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, 985 + ... + 6504.

It is an arithmetic number, because the mean of its divisors is an integer number (1011150).

Almost surely, 2^20669640 is an apocalyptic number.

20669640 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 20669640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32356800).

20669640 is an abundant number, since it is smaller than the sum of its proper divisors (44043960).

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

20669640 is a wasteful number, since it uses less digits than its factorization.

20669640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7526 (or 7522 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 33.

The square root of 20669640 is about 4546.3875769670. The cubic root of 20669640 is about 274.4380369828.

The spelling of 20669640 in words is "twenty million, six hundred sixty-nine thousand, six hundred forty".