1621705221 has 12 divisors (see below), whose sum is σ = 2342815020. Its totient is φ = 1080974400.

The previous prime is 1621705133. The next prime is 1621705231. The reversal of 1621705221 is 1225071261.

It can be written as a sum of positive squares in 2 ways, for example, as 797441121 + 824264100 = 28239^2 + 28710^2 .

It is not a de Polignac number, because 1621705221 - 2¹⁵ = 1621672453 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621705231) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 98575 + ... + 113843.

It is an arithmetic number, because the mean of its divisors is an integer number (195234585).

Almost surely, 2^1621705221 is an apocalyptic number.

It is an amenable number.

1621705221 is a deficient number, since it is larger than the sum of its proper divisors (721109799).

1621705221 is a wasteful number, since it uses less digits than its factorization.

1621705221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27076 (or 27073 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 1621705221 is about 40270.4013017005. The cubic root of 1621705221 is about 1174.8722289917.

Adding to 1621705221 its reverse (1225071261), we get a palindrome (2846776482).

The spelling of 1621705221 in words is "one billion, six hundred twenty-one million, seven hundred five thousand, two hundred twenty-one".