61981523257 has 4 divisors (see below), whose sum is σ = 62000045136. Its totient is φ = 61963001380.

The previous prime is 61981523249. The next prime is 61981523267. The reversal of 61981523257 is 75232518916.

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 61981523257 - 2³ = 61981523249 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 61981523257.

It is not an unprimeable number, because it can be changed into a prime (61981523207) 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, 9255919 + ... + 9262612.

It is an arithmetic number, because the mean of its divisors is an integer number (15500011284).

Almost surely, 2^61981523257 is an apocalyptic number.

It is an amenable number.

61981523257 is a deficient number, since it is larger than the sum of its proper divisors (18521879).

61981523257 is a wasteful number, since it uses less digits than its factorization.

61981523257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18521878.

The product of its digits is 907200, while the sum is 49.

The spelling of 61981523257 in words is "sixty-one billion, nine hundred eighty-one million, five hundred twenty-three thousand, two hundred fifty-seven".