215605421 has 2 divisors, whose sum is σ = 215605422. Its totient is φ = 215605420.

The previous prime is 215605409. The next prime is 215605447. The reversal of 215605421 is 124506512.

It is an a-pointer prime, because the next prime (215605447) can be obtained adding 215605421 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 115885225 + 99720196 = 10765^2 + 9986^2 .

It is a cyclic number.

It is not a de Polignac number, because 215605421 - 2¹⁴ = 215589037 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215605451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107802710 + 107802711.

It is an arithmetic number, because the mean of its divisors is an integer number (107802711).

Almost surely, 2^215605421 is an apocalyptic number.

It is an amenable number.

215605421 is a deficient number, since it is larger than the sum of its proper divisors (1).

215605421 is an equidigital number, since it uses as much as digits as its factorization.

215605421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 215605421 is about 14683.5084703895. The cubic root of 215605421 is about 599.6344263792.

The spelling of 215605421 in words is "two hundred fifteen million, six hundred five thousand, four hundred twenty-one".