20491880 has 64 divisors (see below), whose sum is σ = 49464000. Its totient is φ = 7617024.

The previous prime is 20491853. The next prime is 20491897. The reversal of 20491880 is 8819402.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 44612 + ... + 45068.

It is an arithmetic number, because the mean of its divisors is an integer number (772875).

Almost surely, 2^20491880 is an apocalyptic number.

20491880 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 20491880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24732000).

20491880 is an abundant number, since it is smaller than the sum of its proper divisors (28972120).

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

20491880 is a wasteful number, since it uses less digits than its factorization.

20491880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546 (or 542 counting only the distinct ones).

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

The square root of 20491880 is about 4526.7957762638. The cubic root of 20491880 is about 273.6490436232.

The spelling of 20491880 in words is "twenty million, four hundred ninety-one thousand, eight hundred eighty".