1621705220 has 48 divisors (see below), whose sum is σ = 3459017520. Its totient is φ = 638539776.

The previous prime is 1621705133. The next prime is 1621705231. The reversal of 1621705220 is 225071261.

It can be written as a sum of positive squares in 8 ways, for example, as 397125184 + 1224580036 = 19928^2 + 34994^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 1621705220.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1180454 + ... + 1181826.

It is an arithmetic number, because the mean of its divisors is an integer number (72062865).

Almost surely, 2^1621705220 is an apocalyptic number.

1621705220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1621705220 is an abundant number, since it is smaller than the sum of its proper divisors (1837312300).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1621705220 is a wasteful number, since it uses less digits than its factorization.

1621705220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2264 (or 2262 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 1621705220 is about 40270.4012892844. The cubic root of 1621705220 is about 1174.8722287502.

Adding to 1621705220 its reverse (225071261), we get a palindrome (1846776481).

The spelling of 1621705220 in words is "one billion, six hundred twenty-one million, seven hundred five thousand, two hundred twenty".