20671640 has 48 divisors (see below), whose sum is σ = 51135840. Its totient is φ = 7515200.

The previous prime is 20671631. The next prime is 20671649. The reversal of 20671640 is 4617602.

20671640 = T₃₉₄ + T₃₉₅ + ... + T₅₆₉.

It is an interprime number because it is at equal distance from previous prime (20671631) and next prime (20671649).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20671649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2705 + ... + 6975.

It is an arithmetic number, because the mean of its divisors is an integer number (1065330).

Almost surely, 2^20671640 is an apocalyptic number.

20671640 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 20671640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25567920).

20671640 is an abundant number, since it is smaller than the sum of its proper divisors (30464200).

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

20671640 is a wasteful number, since it uses less digits than its factorization.

20671640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4304 (or 4289 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 26.

The square root of 20671640 is about 4546.6075264971. The cubic root of 20671640 is about 274.4468882637.

The spelling of 20671640 in words is "twenty million, six hundred seventy-one thousand, six hundred forty".