1621445661 has 16 divisors (see below), whose sum is σ = 2620518720. Its totient is φ = 982694160.

The previous prime is 1621445659. The next prime is 1621445719. The reversal of 1621445661 is 1665441261.

It is not a de Polignac number, because 1621445661 - 2¹ = 1621445659 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621440661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2729410 + ... + 2730003.

It is an arithmetic number, because the mean of its divisors is an integer number (163782420).

Almost surely, 2^1621445661 is an apocalyptic number.

1621445661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1621445661 is a deficient number, since it is larger than the sum of its proper divisors (999073059).

1621445661 is a wasteful number, since it uses less digits than its factorization.

1621445661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5459433 (or 5459427 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The square root of 1621445661 is about 40267.1784583921. The cubic root of 1621445661 is about 1174.8095447458.

The spelling of 1621445661 in words is "one billion, six hundred twenty-one million, four hundred forty-five thousand, six hundred sixty-one".