1261566401 has 2 divisors, whose sum is σ = 1261566402. Its totient is φ = 1261566400.

The previous prime is 1261566337. The next prime is 1261566431. The reversal of 1261566401 is 1046651621.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1254930625 + 6635776 = 35425^2 + 2576^2 .

It is a cyclic number.

It is not a de Polignac number, because 1261566401 - 2⁶ = 1261566337 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (1261566431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 630783200 + 630783201.

It is an arithmetic number, because the mean of its divisors is an integer number (630783201).

Almost surely, 2^1261566401 is an apocalyptic number.

It is an amenable number.

1261566401 is a deficient number, since it is larger than the sum of its proper divisors (1).

1261566401 is an equidigital number, since it uses as much as digits as its factorization.

1261566401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8640, while the sum is 32.

The square root of 1261566401 is about 35518.5360199432. The cubic root of 1261566401 is about 1080.5296901575.

The spelling of 1261566401 in words is "one billion, two hundred sixty-one million, five hundred sixty-six thousand, four hundred one".