21798987 has 8 divisors (see below), whose sum is σ = 33217536. Its totient is φ = 12456552.

The previous prime is 21798971. The next prime is 21798991. The reversal of 21798987 is 78989712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21798987 - 2⁴ = 21798971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21798967) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 519003 + ... + 519044.

It is an arithmetic number, because the mean of its divisors is an integer number (4152192).

Almost surely, 2^21798987 is an apocalyptic number.

21798987 is a deficient number, since it is larger than the sum of its proper divisors (11418549).

21798987 is a wasteful number, since it uses less digits than its factorization.

21798987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1038057.

The product of its digits is 508032, while the sum is 51.

The square root of 21798987 is about 4668.9385303300. The cubic root of 21798987 is about 279.3479170880.

The spelling of 21798987 in words is "twenty-one million, seven hundred ninety-eight thousand, nine hundred eighty-seven".