21894815891 has 8 divisors (see below), whose sum is σ = 24604208160. Its totient is φ = 19331877312.

The previous prime is 21894815861. The next prime is 21894815963. The reversal of 21894815891 is 19851849812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21894815891 - 2³⁰ = 20821074067 is a prime.

It is a super-2 number, since 2×21894815891² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21894815861) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36613106 + ... + 36613703.

It is an arithmetic number, because the mean of its divisors is an integer number (3075526020).

Almost surely, 2^21894815891 is an apocalyptic number.

21894815891 is a deficient number, since it is larger than the sum of its proper divisors (2709392269).

21894815891 is a wasteful number, since it uses less digits than its factorization.

21894815891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73226845.

The product of its digits is 1658880, while the sum is 56.

The spelling of 21894815891 in words is "twenty-one billion, eight hundred ninety-four million, eight hundred fifteen thousand, eight hundred ninety-one".