21951778531 has 2 divisors, whose sum is σ = 21951778532. Its totient is φ = 21951778530.

The previous prime is 21951778523. The next prime is 21951778543. The reversal of 21951778531 is 13587715912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21951778531 - 2³ = 21951778523 is a prime.

It is a super-2 number, since 2×21951778531² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21951778591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10975889265 + 10975889266.

It is an arithmetic number, because the mean of its divisors is an integer number (10975889266).

Almost surely, 2^21951778531 is an apocalyptic number.

21951778531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21951778531 is an equidigital number, since it uses as much as digits as its factorization.

21951778531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 529200, while the sum is 49.

The spelling of 21951778531 in words is "twenty-one billion, nine hundred fifty-one million, seven hundred seventy-eight thousand, five hundred thirty-one".