1261321997 has 8 divisors (see below), whose sum is σ = 1361844120. Its totient is φ = 1161299520.

The previous prime is 1261321951. The next prime is 1261322009. The reversal of 1261321997 is 7991231621.

It can be written as a sum of positive squares in 4 ways, for example, as 59382436 + 1201939561 = 7706^2 + 34669^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1261321997 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261321907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 119654 + ... + 129767.

It is an arithmetic number, because the mean of its divisors is an integer number (170230515).

Almost surely, 2^1261321997 is an apocalyptic number.

It is an amenable number.

1261321997 is a deficient number, since it is larger than the sum of its proper divisors (100522123).

1261321997 is a wasteful number, since it uses less digits than its factorization.

1261321997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 249823.

The product of its digits is 40824, while the sum is 41.

The square root of 1261321997 is about 35515.0953398692. The cubic root of 1261321997 is about 1080.4599084338.

The spelling of 1261321997 in words is "one billion, two hundred sixty-one million, three hundred twenty-one thousand, nine hundred ninety-seven".