6451561621 has 4 divisors (see below), whose sum is σ = 6659676544. Its totient is φ = 6243446700.

The previous prime is 6451561609. The next prime is 6451561637. The reversal of 6451561621 is 1261651546.

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 a de Polignac number, because none of the positive numbers 2^k-6451561621 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 (6451561021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 104057415 + ... + 104057476.

It is an arithmetic number, because the mean of its divisors is an integer number (1664919136).

Almost surely, 2^6451561621 is an apocalyptic number.

It is an amenable number.

6451561621 is a deficient number, since it is larger than the sum of its proper divisors (208114923).

6451561621 is a wasteful number, since it uses less digits than its factorization.

6451561621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208114922.

The product of its digits is 43200, while the sum is 37.

The square root of 6451561621 is about 80321.6136603343. The cubic root of 6451561621 is about 1861.6081999121.

The spelling of 6451561621 in words is "six billion, four hundred fifty-one million, five hundred sixty-one thousand, six hundred twenty-one".