21951525787 has 4 divisors (see below), whose sum is σ = 21951877320. Its totient is φ = 21951174256.

The previous prime is 21951525767. The next prime is 21951525821. The reversal of 21951525787 is 78752515912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21951525787 is a prime.

It is a super-3 number, since 3×21951525787³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21951525767) 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 in 3 ways as a sum of consecutive naturals, for example, 53962 + ... + 216367.

It is an arithmetic number, because the mean of its divisors is an integer number (5487969330).

Almost surely, 2^21951525787 is an apocalyptic number.

21951525787 is a deficient number, since it is larger than the sum of its proper divisors (351533).

21951525787 is an equidigital number, since it uses as much as digits as its factorization.

21951525787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351532.

The product of its digits is 1764000, while the sum is 52.

The spelling of 21951525787 in words is "twenty-one billion, nine hundred fifty-one million, five hundred twenty-five thousand, seven hundred eighty-seven".