25717561978 has 16 divisors (see below), whose sum is σ = 39938625000. Its totient is φ = 12405399552.

The previous prime is 25717561927. The next prime is 25717561981. The reversal of 25717561978 is 87916571752.

It can be written as a sum of positive squares in 4 ways, for example, as 15861639249 + 9855922729 = 125943^2 + 99277^2 .

It is a super-2 number, since 2×25717561978² (a number of 22 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (58).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 105063 + ... + 249946.

Almost surely, 2^25717561978 is an apocalyptic number.

25717561978 is a deficient number, since it is larger than the sum of its proper divisors (14221063022).

25717561978 is a wasteful number, since it uses less digits than its factorization.

25717561978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 356289.

The product of its digits is 7408800, while the sum is 58.

The spelling of 25717561978 in words is "twenty-five billion, seven hundred seventeen million, five hundred sixty-one thousand, nine hundred seventy-eight".