21586381 has 2 divisors, whose sum is σ = 21586382. Its totient is φ = 21586380.

The previous prime is 21586373. The next prime is 21586393. The reversal of 21586381 is 18368512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14516100 + 7070281 = 3810^2 + 2659^2 .

It is a cyclic number.

It is not a de Polignac number, because 21586381 - 2³ = 21586373 is a prime.

It is a super-2 number, since 2×21586381² = 931943689354322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21586321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10793190 + 10793191.

It is an arithmetic number, because the mean of its divisors is an integer number (10793191).

Almost surely, 2^21586381 is an apocalyptic number.

It is an amenable number.

21586381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21586381 is an equidigital number, since it uses as much as digits as its factorization.

21586381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11520, while the sum is 34.

The square root of 21586381 is about 4646.1146133086. The cubic root of 21586381 is about 278.4367864162.

The spelling of 21586381 in words is "twenty-one million, five hundred eighty-six thousand, three hundred eighty-one".