21961246787 has 4 divisors (see below), whose sum is σ = 22178684976. Its totient is φ = 21743808600.

The previous prime is 21961246771. The next prime is 21961246793. The reversal of 21961246787 is 78764216912.

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

It is a cyclic number.

It is not a de Polignac number, because 21961246787 - 2⁴ = 21961246771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21961246717) 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, 108718943 + ... + 108719144.

It is an arithmetic number, because the mean of its divisors is an integer number (5544671244).

Almost surely, 2^21961246787 is an apocalyptic number.

21961246787 is a deficient number, since it is larger than the sum of its proper divisors (217438189).

21961246787 is a wasteful number, since it uses less digits than its factorization.

21961246787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217438188.

The product of its digits is 2032128, while the sum is 53.

The spelling of 21961246787 in words is "twenty-one billion, nine hundred sixty-one million, two hundred forty-six thousand, seven hundred eighty-seven".