1621766656 has 20 divisors (see below), whose sum is σ = 3240366822. Its totient is φ = 810883072.

The previous prime is 1621766609. The next prime is 1621766659. The reversal of 1621766656 is 6566671261.

It can be written as a sum of positive squares in only one way, i.e., 1619257600 + 2509056 = 40240^2 + 1584^2 .

It is not an unprimeable number, because it can be changed into a prime (1621766659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1583245 + ... + 1584268.

Almost surely, 2^1621766656 is an apocalyptic number.

1621766656 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

1621766656 is a deficient number, since it is larger than the sum of its proper divisors (1618600166).

1621766656 is an frugal number, since it uses more digits than its factorization.

1621766656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3167531 (or 3167515 counting only the distinct ones).

The product of its digits is 544320, while the sum is 46.

The square root of 1621766656 is about 40271.1640755516. The cubic root of 1621766656 is about 1174.8870646850.

The spelling of 1621766656 in words is "one billion, six hundred twenty-one million, seven hundred sixty-six thousand, six hundred fifty-six".