21389051 has 4 divisors (see below), whose sum is σ = 21792672. Its totient is φ = 20985432.

The previous prime is 21389021. The next prime is 21389059. The reversal of 21389051 is 15098312.

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 21389051 - 2⁶ = 21388987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21389059) 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, 201731 + ... + 201836.

It is an arithmetic number, because the mean of its divisors is an integer number (5448168).

Almost surely, 2^21389051 is an apocalyptic number.

21389051 is a deficient number, since it is larger than the sum of its proper divisors (403621).

21389051 is an equidigital number, since it uses as much as digits as its factorization.

21389051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 403620.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 21389051 is about 4624.8298347074. The cubic root of 21389051 is about 277.5857527908.

The spelling of 21389051 in words is "twenty-one million, three hundred eighty-nine thousand, fifty-one".