1261728396421 has 4 divisors (see below), whose sum is σ = 1291070917312. Its totient is φ = 1232385875532.

The previous prime is 1261728396413. The next prime is 1261728396443. The reversal of 1261728396421 is 1246938271621.

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 a cyclic number.

It is not a de Polignac number, because 1261728396421 - 2³ = 1261728396413 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261728396491) 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, 14671260381 + ... + 14671260466.

It is an arithmetic number, because the mean of its divisors is an integer number (322767729328).

Almost surely, 2^{1261728396421} is an apocalyptic number.

It is an amenable number.

1261728396421 is a deficient number, since it is larger than the sum of its proper divisors (29342520891).

1261728396421 is an equidigital number, since it uses as much as digits as its factorization.

1261728396421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29342520890.

The product of its digits is 1741824, while the sum is 52.

The spelling of 1261728396421 in words is "one trillion, two hundred sixty-one billion, seven hundred twenty-eight million, three hundred ninety-six thousand, four hundred twenty-one".