1261639 has 2 divisors, whose sum is σ = 1261640. Its totient is φ = 1261638.

The previous prime is 1261627. The next prime is 1261643. The reversal of 1261639 is 9361621.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1261639 - 2¹⁹ = 737351 is a prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1261649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630819 + 630820.

It is an arithmetic number, because the mean of its divisors is an integer number (630820).

2^1261639 is an apocalyptic number.

1261639 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261639 is an equidigital number, since it uses as much as digits as its factorization.

1261639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1944, while the sum is 28.

The square root of 1261639 is about 1123.2270473951. The cubic root of 1261639 is about 108.0550416737.

The spelling of 1261639 in words is "one million, two hundred sixty-one thousand, six hundred thirty-nine".