61681819 has 2 divisors, whose sum is σ = 61681820. Its totient is φ = 61681818.

The previous prime is 61681817. The next prime is 61681843. The reversal of 61681819 is 91818616.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 61681819 - 2¹ = 61681817 is a prime.

It is a super-2 number, since 2×61681819² = 7609293590297522, which contains 22 as substring.

Together with 61681817, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (61681817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30840909 + 30840910.

It is an arithmetic number, because the mean of its divisors is an integer number (30840910).

Almost surely, 2^61681819 is an apocalyptic number.

61681819 is a deficient number, since it is larger than the sum of its proper divisors (1).

61681819 is an equidigital number, since it uses as much as digits as its factorization.

61681819 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 40.

The square root of 61681819 is about 7853.7773714309. Note that the first 3 decimals coincide. The cubic root of 61681819 is about 395.1109425057.

It can be divided in two parts, 61681 and 819, that added together give a square (62500 = 250²).

The spelling of 61681819 in words is "sixty-one million, six hundred eighty-one thousand, eight hundred nineteen".