21896987 has 16 divisors (see below), whose sum is σ = 26784000. Its totient is φ = 17483040.

The previous prime is 21896951. The next prime is 21896999. The reversal of 21896987 is 78969812.

It is a de Polignac number, because none of the positive numbers 2^k-21896987 is a prime.

It is a Smith number, since the sum of its digits (50) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21896387) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6764 + ... + 9462.

It is an arithmetic number, because the mean of its divisors is an integer number (1674000).

Almost surely, 2^21896987 is an apocalyptic number.

21896987 is a deficient number, since it is larger than the sum of its proper divisors (4887013).

21896987 is a wasteful number, since it uses less digits than its factorization.

21896987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2786.

The product of its digits is 435456, while the sum is 50.

The square root of 21896987 is about 4679.4216522985. The cubic root of 21896987 is about 279.7659055299.

The spelling of 21896987 in words is "twenty-one million, eight hundred ninety-six thousand, nine hundred eighty-seven".