21295918987 has 4 divisors (see below), whose sum is σ = 24338193136. Its totient is φ = 18253644840.

The previous prime is 21295918981. The next prime is 21295919009. The reversal of 21295918987 is 78981959212.

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 21295918987 - 2⁷ = 21295918859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21295918981) 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, 1521137064 + ... + 1521137077.

It is an arithmetic number, because the mean of its divisors is an integer number (6084548284).

Almost surely, 2^21295918987 is an apocalyptic number.

21295918987 is a deficient number, since it is larger than the sum of its proper divisors (3042274149).

21295918987 is an equidigital number, since it uses as much as digits as its factorization.

21295918987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3042274148.

The product of its digits is 6531840, while the sum is 61.

The spelling of 21295918987 in words is "twenty-one billion, two hundred ninety-five million, nine hundred eighteen thousand, nine hundred eighty-seven".