20858640 has 80 divisors (see below), whose sum is σ = 70549056. Its totient is φ = 5056000.

The previous prime is 20858611. The next prime is 20858653. The reversal of 20858640 is 4685802.

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

It is a Harshad number since it is a multiple of its sum of digits (33).

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 15 ways as a sum of consecutive naturals, for example, 1311 + ... + 6590.

Almost surely, 2^20858640 is an apocalyptic number.

20858640 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 20858640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35274528).

20858640 is an abundant number, since it is smaller than the sum of its proper divisors (49690416).

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

20858640 is a wasteful number, since it uses less digits than its factorization.

20858640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7928 (or 7922 counting only the distinct ones).

The product of its (nonzero) digits is 15360, while the sum is 33.

The square root of 20858640 is about 4567.1260109614. The cubic root of 20858640 is about 275.2719733555.

The spelling of 20858640 in words is "twenty million, eight hundred fifty-eight thousand, six hundred forty".