21788487 has 48 divisors (see below), whose sum is σ = 38522880. Its totient is φ = 12129264.

The previous prime is 21788479. The next prime is 21788491. The reversal of 21788487 is 78488712.

It is not a de Polignac number, because 21788487 - 2³ = 21788479 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21788447) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 56698 + ... + 57080.

It is an arithmetic number, because the mean of its divisors is an integer number (802560).

Almost surely, 2^21788487 is an apocalyptic number.

21788487 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21788487 is a deficient number, since it is larger than the sum of its proper divisors (16734393).

21788487 is a wasteful number, since it uses less digits than its factorization.

21788487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 449 (or 436 counting only the distinct ones).

The product of its digits is 200704, while the sum is 45.

The square root of 21788487 is about 4667.8139423075. The cubic root of 21788487 is about 279.3030583644.

The spelling of 21788487 in words is "twenty-one million, seven hundred eighty-eight thousand, four hundred eighty-seven".