1620402661 has 4 divisors (see below), whose sum is σ = 1620585792. Its totient is φ = 1620219532.

The previous prime is 1620402653. The next prime is 1620402703. The reversal of 1620402661 is 1662040261.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1620402661 - 2³ = 1620402653 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 (1620403661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 77581 + ... + 96226.

It is an arithmetic number, because the mean of its divisors is an integer number (405146448).

Almost surely, 2^1620402661 is an apocalyptic number.

It is an amenable number.

1620402661 is a deficient number, since it is larger than the sum of its proper divisors (183131).

1620402661 is an equidigital number, since it uses as much as digits as its factorization.

1620402661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183130.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 1620402661 is about 40254.2253806976. The cubic root of 1620402661 is about 1174.5575907415.

The spelling of 1620402661 in words is "one billion, six hundred twenty million, four hundred two thousand, six hundred sixty-one".