61321781 has 2 divisors, whose sum is σ = 61321782. Its totient is φ = 61321780.

The previous prime is 61321769. The next prime is 61321783. The reversal of 61321781 is 18712316.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 40436881 + 20884900 = 6359^2 + 4570^2 .

It is a cyclic number.

It is not a de Polignac number, because 61321781 - 2⁶ = 61321717 is a prime.

It is a super-2 number, since 2×61321781² = 7520721650023922, which contains 22 as substring.

Together with 61321783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61321783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30660890 + 30660891.

It is an arithmetic number, because the mean of its divisors is an integer number (30660891).

Almost surely, 2^61321781 is an apocalyptic number.

It is an amenable number.

61321781 is a deficient number, since it is larger than the sum of its proper divisors (1).

61321781 is an equidigital number, since it uses as much as digits as its factorization.

61321781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 29.

The square root of 61321781 is about 7830.8224983076. The cubic root of 61321781 is about 394.3406850861.

The spelling of 61321781 in words is "sixty-one million, three hundred twenty-one thousand, seven hundred eighty-one".