61631781 has 4 divisors (see below), whose sum is σ = 82175712. Its totient is φ = 41087852.

The previous prime is 61631747. The next prime is 61631819. The reversal of 61631781 is 18713616.

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 61631781 - 2¹⁹ = 61107493 is a prime.

It is a super-2 number, since 2×61631781² = 7596952858463922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61631741) 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, 10271961 + ... + 10271966.

It is an arithmetic number, because the mean of its divisors is an integer number (20543928).

Almost surely, 2^61631781 is an apocalyptic number.

It is an amenable number.

61631781 is a deficient number, since it is larger than the sum of its proper divisors (20543931).

61631781 is a wasteful number, since it uses less digits than its factorization.

61631781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20543930.

The product of its digits is 6048, while the sum is 33.

The square root of 61631781 is about 7850.5911242403. The cubic root of 61631781 is about 395.0040719550.

The spelling of 61631781 in words is "sixty-one million, six hundred thirty-one thousand, seven hundred eighty-one".