1296635721 has 16 divisors (see below), whose sum is σ = 1735991040. Its totient is φ = 860861520.

The previous prime is 1296635719. The next prime is 1296635771. The reversal of 1296635721 is 1275366921.

It is not a de Polignac number, because 1296635721 - 2¹ = 1296635719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1296635771) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1271950 + ... + 1272968.

It is an arithmetic number, because the mean of its divisors is an integer number (108499440).

Almost surely, 2^1296635721 is an apocalyptic number.

It is an amenable number.

1296635721 is a deficient number, since it is larger than the sum of its proper divisors (439355319).

1296635721 is a wasteful number, since it uses less digits than its factorization.

1296635721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2356.

The product of its digits is 136080, while the sum is 42.

The square root of 1296635721 is about 36008.8283758303. The cubic root of 1296635721 is about 1090.4505953428.

The spelling of 1296635721 in words is "one billion, two hundred ninety-six million, six hundred thirty-five thousand, seven hundred twenty-one".