1261388649 has 4 divisors (see below), whose sum is σ = 1681851536. Its totient is φ = 840925764.

The previous prime is 1261388633. The next prime is 1261388759. The reversal of 1261388649 is 9468831621.

1261388649 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1261388649 - 2⁴ = 1261388633 is a prime.

It is a super-2 number, since 2×1261388649² = 3182202647652090402, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1261388598 and 1261388607.

It is not an unprimeable number, because it can be changed into a prime (1261388629) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 210231439 + ... + 210231444.

It is an arithmetic number, because the mean of its divisors is an integer number (420462884).

Almost surely, 2^1261388649 is an apocalyptic number.

It is an amenable number.

1261388649 is a deficient number, since it is larger than the sum of its proper divisors (420462887).

1261388649 is an equidigital number, since it uses as much as digits as its factorization.

1261388649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 420462886.

The product of its digits is 497664, while the sum is 48.

The square root of 1261388649 is about 35516.0336890256. The cubic root of 1261388649 is about 1080.4789396687.

The spelling of 1261388649 in words is "one billion, two hundred sixty-one million, three hundred eighty-eight thousand, six hundred forty-nine".