61945781 has 4 divisors (see below), whose sum is σ = 63944064. Its totient is φ = 59947500.

The previous prime is 61945777. The next prime is 61945789. The reversal of 61945781 is 18754916.

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 not a de Polignac number, because 61945781 - 2² = 61945777 is a prime.

It is a super-2 number, since 2×61945781² = 7674559567399922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61945789) 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, 999095 + ... + 999156.

It is an arithmetic number, because the mean of its divisors is an integer number (15986016).

Almost surely, 2^61945781 is an apocalyptic number.

It is an amenable number.

61945781 is a deficient number, since it is larger than the sum of its proper divisors (1998283).

61945781 is a wasteful number, since it uses less digits than its factorization.

61945781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1998282.

The product of its digits is 60480, while the sum is 41.

The square root of 61945781 is about 7870.5642110334. The cubic root of 61945781 is about 395.6737547802.

It can be divided in two parts, 61945 and 781, that added together give a palindrome (62726).

The spelling of 61945781 in words is "sixty-one million, nine hundred forty-five thousand, seven hundred eighty-one".