642216961 has 4 divisors (see below), whose sum is σ = 642394372. Its totient is φ = 642039552.

The previous prime is 642216959. The next prime is 642217003. The reversal of 642216961 is 169612246.

642216961 = 17919² + 17920².

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 321126400 + 321090561 = 17920^2 + 17919^2 .

It is a cyclic number.

It is not a de Polignac number, because 642216961 - 2¹ = 642216959 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 642216961.

It is not an unprimeable number, because it can be changed into a prime (642216901) 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, 83160 + ... + 90553.

It is an arithmetic number, because the mean of its divisors is an integer number (160598593).

Almost surely, 2^642216961 is an apocalyptic number.

642216961 is the 17920-th centered square number.

It is an amenable number.

642216961 is a deficient number, since it is larger than the sum of its proper divisors (177411).

642216961 is a wasteful number, since it uses less digits than its factorization.

642216961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177410.

The product of its digits is 31104, while the sum is 37.

The square root of 642216961 is about 25341.9999408097. Note that the first 4 decimals coincide. The cubic root of 642216961 is about 862.7677912710.

The spelling of 642216961 in words is "six hundred forty-two million, two hundred sixteen thousand, nine hundred sixty-one".