1242001721 has 4 divisors (see below), whose sum is σ = 1242195492. Its totient is φ = 1241807952.

The previous prime is 1242001697. The next prime is 1242001729. The reversal of 1242001721 is 1271002421.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1271002421 = 13 ⋅97769417.

It can be written as a sum of positive squares in 2 ways, for example, as 152275600 + 1089726121 = 12340^2 + 33011^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1242001721 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1242001693 and 1242001702.

It is not an unprimeable number, because it can be changed into a prime (1242001729) 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, 86930 + ... + 100203.

It is an arithmetic number, because the mean of its divisors is an integer number (310548873).

Almost surely, 2^1242001721 is an apocalyptic number.

It is an amenable number.

1242001721 is a deficient number, since it is larger than the sum of its proper divisors (193771).

1242001721 is an equidigital number, since it uses as much as digits as its factorization.

1242001721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193770.

The product of its (nonzero) digits is 224, while the sum is 20.

The square root of 1242001721 is about 35242.0447902786. The cubic root of 1242001721 is about 1074.9148577961.

The spelling of 1242001721 in words is "one billion, two hundred forty-two million, one thousand, seven hundred twenty-one".