261387421 has 2 divisors, whose sum is σ = 261387422. Its totient is φ = 261387420.

The previous prime is 261387403. The next prime is 261387431. The reversal of 261387421 is 124783162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 255680100 + 5707321 = 15990^2 + 2389^2 .

It is a cyclic number.

It is not a de Polignac number, because 261387421 - 2¹⁹ = 260863133 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261387431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130693710 + 130693711.

It is an arithmetic number, because the mean of its divisors is an integer number (130693711).

Almost surely, 2^261387421 is an apocalyptic number.

It is an amenable number.

261387421 is a deficient number, since it is larger than the sum of its proper divisors (1).

261387421 is an equidigital number, since it uses as much as digits as its factorization.

261387421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16128, while the sum is 34.

The square root of 261387421 is about 16167.4803540935. The cubic root of 261387421 is about 639.3837011487.

The spelling of 261387421 in words is "two hundred sixty-one million, three hundred eighty-seven thousand, four hundred twenty-one".