1621560661 has 8 divisors (see below), whose sum is σ = 1884623040. Its totient is φ = 1366351008.

The previous prime is 1621560649. The next prime is 1621560673. The reversal of 1621560661 is 1660651261.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1621560649) and next prime (1621560673).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1621560661 - 2¹¹ = 1621558613 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621560641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1962736 + ... + 1963561.

It is an arithmetic number, because the mean of its divisors is an integer number (235577880).

Almost surely, 2^1621560661 is an apocalyptic number.

It is an amenable number.

1621560661 is a deficient number, since it is larger than the sum of its proper divisors (263062379).

1621560661 is an equidigital number, since it uses as much as digits as its factorization.

1621560661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3926363.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 1621560661 is about 40268.6063950567. The cubic root of 1621560661 is about 1174.8373182952.

The spelling of 1621560661 in words is "one billion, six hundred twenty-one million, five hundred sixty thousand, six hundred sixty-one".