20891840 has 28 divisors (see below), whose sum is σ = 49749456. Its totient is φ = 8356608.

The previous prime is 20891831. The next prime is 20891879. The reversal of 20891840 is 4819802.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 20891797 and 20891806.

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 3 ways as a sum of consecutive naturals, for example, 32324 + ... + 32963.

Almost surely, 2^20891840 is an apocalyptic number.

20891840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20891840 is an abundant number, since it is smaller than the sum of its proper divisors (28857616).

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

20891840 is an equidigital number, since it uses as much as digits as its factorization.

20891840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65304 (or 65294 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 20891840 is about 4570.7592367133. The cubic root of 20891840 is about 275.4179430039.

The spelling of 20891840 in words is "twenty million, eight hundred ninety-one thousand, eight hundred forty".