21864787 has 4 divisors (see below), whose sum is σ = 24988336. Its totient is φ = 18741240.

The previous prime is 21864761. The next prime is 21864797. The reversal of 21864787 is 78746812.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21864787 - 2⁷ = 21864659 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21864757) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1561764 + ... + 1561777.

It is an arithmetic number, because the mean of its divisors is an integer number (6247084).

Almost surely, 2^21864787 is an apocalyptic number.

21864787 is a deficient number, since it is larger than the sum of its proper divisors (3123549).

21864787 is an equidigital number, since it uses as much as digits as its factorization.

21864787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3123548.

The product of its digits is 150528, while the sum is 43.

The square root of 21864787 is about 4675.9797903755. The cubic root of 21864787 is about 279.6287042873.

The spelling of 21864787 in words is "twenty-one million, eight hundred sixty-four thousand, seven hundred eighty-seven".