1656620645 has 4 divisors (see below), whose sum is σ = 1987944780. Its totient is φ = 1325296512.

The previous prime is 1656620633. The next prime is 1656620653. The reversal of 1656620645 is 5460266561.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 248945284 + 1407675361 = 15778^2 + 37519^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1656620645 is a prime.

It is a super-2 number, since 2×1656620645² = 5488783922880432050, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 165662060 + ... + 165662069.

It is an arithmetic number, because the mean of its divisors is an integer number (496986195).

Almost surely, 2^1656620645 is an apocalyptic number.

It is an amenable number.

1656620645 is a deficient number, since it is larger than the sum of its proper divisors (331324135).

1656620645 is an equidigital number, since it uses as much as digits as its factorization.

1656620645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 331324134.

The product of its (nonzero) digits is 259200, while the sum is 41.

The square root of 1656620645 is about 40701.6049437857. The cubic root of 1656620645 is about 1183.2441239808.

The spelling of 1656620645 in words is "one billion, six hundred fifty-six million, six hundred twenty thousand, six hundred forty-five".