21987011 has 4 divisors (see below), whose sum is σ = 22942992. Its totient is φ = 21031032.

The previous prime is 21986989. The next prime is 21987019. The reversal of 21987011 is 11078912.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21987011 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21987019) 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, 477956 + ... + 478001.

It is an arithmetic number, because the mean of its divisors is an integer number (5735748).

Almost surely, 2^21987011 is an apocalyptic number.

21987011 is a deficient number, since it is larger than the sum of its proper divisors (955981).

21987011 is an equidigital number, since it uses as much as digits as its factorization.

21987011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 955980.

The product of its (nonzero) digits is 1008, while the sum is 29.

The square root of 21987011 is about 4689.0309233359. The cubic root of 21987011 is about 280.1487772261.

The spelling of 21987011 in words is "twenty-one million, nine hundred eighty-seven thousand, eleven".