21270381 has 8 divisors (see below), whose sum is σ = 30938784. Its totient is φ = 12891120.

The previous prime is 21270373. The next prime is 21270397. The reversal of 21270381 is 18307212.

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

It is not a de Polignac number, because 21270381 - 2³ = 21270373 is a prime.

It is a super-2 number, since 2×21270381² = 904858215770322, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21270181) 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, 322246 + ... + 322311.

It is an arithmetic number, because the mean of its divisors is an integer number (3867348).

Almost surely, 2^21270381 is an apocalyptic number.

It is an amenable number.

21270381 is a deficient number, since it is larger than the sum of its proper divisors (9668403).

21270381 is a wasteful number, since it uses less digits than its factorization.

21270381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 644571.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21270381 is about 4611.9823286739. The cubic root of 21270381 is about 277.0714365229.

Adding to 21270381 its reverse (18307212), we get a palindrome (39577593).

The spelling of 21270381 in words is "twenty-one million, two hundred seventy thousand, three hundred eighty-one".