21387361 has 2 divisors, whose sum is σ = 21387362. Its totient is φ = 21387360.

The previous prime is 21387347. The next prime is 21387389. The reversal of 21387361 is 16378312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15555136 + 5832225 = 3944^2 + 2415^2 .

It is a cyclic number.

It is not a de Polignac number, because 21387361 - 2⁵ = 21387329 is a prime.

It is not a weakly prime, because it can be changed into another prime (21387341) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10693680 + 10693681.

It is an arithmetic number, because the mean of its divisors is an integer number (10693681).

Almost surely, 2^21387361 is an apocalyptic number.

It is an amenable number.

21387361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21387361 is an equidigital number, since it uses as much as digits as its factorization.

21387361 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 31.

The square root of 21387361 is about 4624.6471216732. The cubic root of 21387361 is about 277.5784416939.

The spelling of 21387361 in words is "twenty-one million, three hundred eighty-seven thousand, three hundred sixty-one".