21388711 has 4 divisors (see below), whose sum is σ = 21403000. Its totient is φ = 21374424.

The previous prime is 21388709. The next prime is 21388721. The reversal of 21388711 is 11788312.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21388711 - 2¹ = 21388709 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388721) 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, 4596 + ... + 7993.

It is an arithmetic number, because the mean of its divisors is an integer number (5350750).

Almost surely, 2^21388711 is an apocalyptic number.

21388711 is a deficient number, since it is larger than the sum of its proper divisors (14289).

21388711 is a wasteful number, since it uses less digits than its factorization.

21388711 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14288.

The product of its digits is 2688, while the sum is 31.

The square root of 21388711 is about 4624.7930764522. The cubic root of 21388711 is about 277.5842819502.

The spelling of 21388711 in words is "twenty-one million, three hundred eighty-eight thousand, seven hundred eleven".