20819640 has 32 divisors (see below), whose sum is σ = 62459280. Its totient is φ = 5551872.

The previous prime is 20819639. The next prime is 20819657. The reversal of 20819640 is 4691802.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 20819598 and 20819607.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 86629 + ... + 86868.

Almost surely, 2^20819640 is an apocalyptic number.

20819640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20819640 is an abundant number, since it is smaller than the sum of its proper divisors (41639640).

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

20819640 is a wasteful number, since it uses less digits than its factorization.

20819640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173511 (or 173507 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 20819640 is about 4562.8543697997. The cubic root of 20819640 is about 275.1003050075.

The spelling of 20819640 in words is "twenty million, eight hundred nineteen thousand, six hundred forty".