655721251 has 4 divisors (see below), whose sum is σ = 664021600. Its totient is φ = 647420904.

The previous prime is 655721239. The next prime is 655721257. The reversal of 655721251 is 152127556.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-655721251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (655721257) 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 3 ways as a sum of consecutive naturals, for example, 4150056 + ... + 4150213.

It is an arithmetic number, because the mean of its divisors is an integer number (166005400).

Almost surely, 2^655721251 is an apocalyptic number.

655721251 is a deficient number, since it is larger than the sum of its proper divisors (8300349).

655721251 is an equidigital number, since it uses as much as digits as its factorization.

655721251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8300348.

The product of its digits is 21000, while the sum is 34.

The square root of 655721251 is about 25607.0547115438. The cubic root of 655721251 is about 868.7732085928.

The spelling of 655721251 in words is "six hundred fifty-five million, seven hundred twenty-one thousand, two hundred fifty-one".