61547781 has 4 divisors (see below), whose sum is σ = 82063712. Its totient is φ = 41031852.

The previous prime is 61547779. The next prime is 61547813. The reversal of 61547781 is 18774516.

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 not a de Polignac number, because 61547781 - 2¹ = 61547779 is a prime.

It is a super-2 number, since 2×61547781² = 7576258692047922, 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 (61507781) 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, 10257961 + ... + 10257966.

It is an arithmetic number, because the mean of its divisors is an integer number (20515928).

Almost surely, 2^61547781 is an apocalyptic number.

It is an amenable number.

61547781 is a deficient number, since it is larger than the sum of its proper divisors (20515931).

61547781 is a wasteful number, since it uses less digits than its factorization.

61547781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20515930.

The product of its digits is 47040, while the sum is 39.

The square root of 61547781 is about 7845.2393844930. The cubic root of 61547781 is about 394.8245356448.

The spelling of 61547781 in words is "sixty-one million, five hundred forty-seven thousand, seven hundred eighty-one".