21270391 has 8 divisors (see below), whose sum is σ = 21513600. Its totient is φ = 21028920.

The previous prime is 21270373. The next prime is 21270397. The reversal of 21270391 is 19307212.

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

It is not a de Polignac number, because 21270391 - 2⁹ = 21269879 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 (21270397) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 59070 + ... + 59428.

It is an arithmetic number, because the mean of its divisors is an integer number (2689200).

Almost surely, 2^21270391 is an apocalyptic number.

21270391 is a deficient number, since it is larger than the sum of its proper divisors (243209).

21270391 is a wasteful number, since it uses less digits than its factorization.

21270391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 869.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21270391 is about 4611.9834128063. The cubic root of 21270391 is about 277.0714799434.

The spelling of 21270391 in words is "twenty-one million, two hundred seventy thousand, three hundred ninety-one".