20729840 has 20 divisors (see below), whose sum is σ = 48197064. Its totient is φ = 8291904.

The previous prime is 20729789. The next prime is 20729861. The reversal of 20729840 is 4892702.

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 20729797 and 20729806.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 129482 + ... + 129641.

Almost surely, 2^20729840 is an apocalyptic number.

20729840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20729840 is an abundant number, since it is smaller than the sum of its proper divisors (27467224).

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

20729840 is a wasteful number, since it uses less digits than its factorization.

20729840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259136 (or 259130 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 20729840 is about 4553.0034043475. The cubic root of 20729840 is about 274.7042108899.

The spelling of 20729840 in words is "twenty million, seven hundred twenty-nine thousand, eight hundred forty".