20861778531 has 32 divisors (see below), whose sum is σ = 32199164928. Its totient is φ = 11873917440.

The previous prime is 20861778521. The next prime is 20861778577. The reversal of 20861778531 is 13587716802.

It is a happy number.

It is not a de Polignac number, because 20861778531 - 2¹⁹ = 20861254243 is a prime.

It is a super-2 number, since 2×20861778531² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20861778521) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 219585 + ... + 299901.

It is an arithmetic number, because the mean of its divisors is an integer number (1006223904).

Almost surely, 2^20861778531 is an apocalyptic number.

20861778531 is a deficient number, since it is larger than the sum of its proper divisors (11337386397).

20861778531 is a wasteful number, since it uses less digits than its factorization.

20861778531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80811.

The product of its (nonzero) digits is 564480, while the sum is 48.

The spelling of 20861778531 in words is "twenty billion, eight hundred sixty-one million, seven hundred seventy-eight thousand, five hundred thirty-one".