1247521221 has 6 divisors (see below), whose sum is σ = 1801975110. Its totient is φ = 831680808.

The previous prime is 1247521147. The next prime is 1247521259. The reversal of 1247521221 is 1221257421.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 647957025 + 599564196 = 25455^2 + 24486^2 .

It is not a de Polignac number, because 1247521221 - 2¹¹ = 1247519173 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1247531221) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 69306726 + ... + 69306743.

It is an arithmetic number, because the mean of its divisors is an integer number (300329185).

Almost surely, 2^1247521221 is an apocalyptic number.

It is an amenable number.

1247521221 is a deficient number, since it is larger than the sum of its proper divisors (554453889).

1247521221 is a wasteful number, since it uses less digits than its factorization.

1247521221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138613475 (or 138613472 counting only the distinct ones).

The product of its digits is 2240, while the sum is 27.

The square root of 1247521221 is about 35320.2664344424. The cubic root of 1247521221 is about 1076.5048248313.

Adding to 1247521221 its reverse (1221257421), we get a palindrome (2468778642).

The spelling of 1247521221 in words is "one billion, two hundred forty-seven million, five hundred twenty-one thousand, two hundred twenty-one".