21390771 has 8 divisors (see below), whose sum is σ = 28625104. Its totient is φ = 14208480.

The previous prime is 21390767. The next prime is 21390791. The reversal of 21390771 is 17709312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21390771 - 2² = 21390767 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21390791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12040 + ... + 13701.

It is an arithmetic number, because the mean of its divisors is an integer number (3578138).

Almost surely, 2^21390771 is an apocalyptic number.

21390771 is a deficient number, since it is larger than the sum of its proper divisors (7234333).

21390771 is a wasteful number, since it uses less digits than its factorization.

21390771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26021.

The product of its (nonzero) digits is 2646, while the sum is 30.

The square root of 21390771 is about 4625.0157837569. The cubic root of 21390771 is about 277.5931932752.

The spelling of 21390771 in words is "twenty-one million, three hundred ninety thousand, seven hundred seventy-one".