20987280 has 120 divisors (see below), whose sum is σ = 71418048. Its totient is φ = 5522688.

The previous prime is 20987269. The next prime is 20987287. The reversal of 20987280 is 8278902.

It is a tau number, because it is divible by the number of its divisors (120).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (20987287) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 74019 + ... + 74301.

Almost surely, 2^20987280 is an apocalyptic number.

20987280 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 20987280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35709024).

20987280 is an abundant number, since it is smaller than the sum of its proper divisors (50430768).

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

20987280 is a wasteful number, since it uses less digits than its factorization.

20987280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 405 (or 396 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The square root of 20987280 is about 4581.1876189477. The cubic root of 20987280 is about 275.8367023945.

The spelling of 20987280 in words is "twenty million, nine hundred eighty-seven thousand, two hundred eighty".