1243435651621 has 4 divisors (see below), whose sum is σ = 1243447625644. Its totient is φ = 1243423677600.

The previous prime is 1243435651589. The next prime is 1243435651657. The reversal of 1243435651621 is 1261565343421.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 58191912900 + 1185243738721 = 241230^2 + 1088689^2 .

It is a cyclic number.

It is not a de Polignac number, because 1243435651621 - 2⁵ = 1243435651589 is a prime.

It is a super-2 number, since 2×1243435651621² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1243435651691) 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, 5829870 + ... + 6039391.

It is an arithmetic number, because the mean of its divisors is an integer number (310861906411).

Almost surely, 2^{1243435651621} is an apocalyptic number.

It is an amenable number.

1243435651621 is a deficient number, since it is larger than the sum of its proper divisors (11974023).

1243435651621 is a wasteful number, since it uses less digits than its factorization.

1243435651621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11974022.

The product of its digits is 518400, while the sum is 43.

The spelling of 1243435651621 in words is "one trillion, two hundred forty-three billion, four hundred thirty-five million, six hundred fifty-one thousand, six hundred twenty-one".