21498987 has 6 divisors (see below), whose sum is σ = 28676028. Its totient is φ = 14327304.

The previous prime is 21498977. The next prime is 21498989. The reversal of 21498987 is 78989412.

It is not a de Polignac number, because 21498987 - 2¹⁰ = 21497963 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (21498989) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6693 + ... + 9369.

It is an arithmetic number, because the mean of its divisors is an integer number (4779338).

Almost surely, 2^21498987 is an apocalyptic number.

21498987 is a deficient number, since it is larger than the sum of its proper divisors (7177041).

21498987 is an frugal number, since it uses more digits than its factorization.

21498987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5357 (or 2680 counting only the distinct ones).

The product of its digits is 290304, while the sum is 48.

The square root of 21498987 is about 4636.7000118619. The cubic root of 21498987 is about 278.0605211298.

Multiplying 21498987 by its sum of digits (48), we get a square (1031951376 = 32124²).

The spelling of 21498987 in words is "twenty-one million, four hundred ninety-eight thousand, nine hundred eighty-seven".