21388069 has 4 divisors (see below), whose sum is σ = 21542080. Its totient is φ = 21234060.

The previous prime is 21388049. The next prime is 21388099. The reversal of 21388069 is 96088312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21388069 - 2⁹ = 21387557 is a prime.

It is a super-2 number, since 2×21388069² = 914898991097522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388009) 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, 76797 + ... + 77074.

It is an arithmetic number, because the mean of its divisors is an integer number (5385520).

Almost surely, 2^21388069 is an apocalyptic number.

It is an amenable number.

21388069 is a deficient number, since it is larger than the sum of its proper divisors (154011).

21388069 is a wasteful number, since it uses less digits than its factorization.

21388069 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154010.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21388069 is about 4624.7236674206. The cubic root of 21388069 is about 277.5815046145.

The spelling of 21388069 in words is "twenty-one million, three hundred eighty-eight thousand, sixty-nine".