20715640 has 96 divisors (see below), whose sum is σ = 53751600. Its totient is φ = 7124480.

The previous prime is 20715623. The next prime is 20715641. The reversal of 20715640 is 4651702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20715641) by changing a digit.

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, 232716 + ... + 232804.

Almost surely, 2^20715640 is an apocalyptic number.

20715640 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 20715640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26875800).

20715640 is an abundant number, since it is smaller than the sum of its proper divisors (33035960).

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

20715640 is a wasteful number, since it uses less digits than its factorization.

20715640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 20715640 is about 4551.4437269948. The cubic root of 20715640 is about 274.6414721709.

The spelling of 20715640 in words is "twenty million, seven hundred fifteen thousand, six hundred forty".