21691968 has 28 divisors (see below), whose sum is σ = 57393840. Its totient is φ = 7230592.

The previous prime is 21691963. The next prime is 21691973. The reversal of 21691968 is 86919612.

It is an interprime number because it is at equal distance from previous prime (21691963) and next prime (21691973).

It is not an unprimeable number, because it can be changed into a prime (21691963) 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, 56298 + ... + 56681.

It is an arithmetic number, because the mean of its divisors is an integer number (2049780).

Almost surely, 2^21691968 is an apocalyptic number.

It is an amenable number.

21691968 is an abundant number, since it is smaller than the sum of its proper divisors (35701872).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21691968 is a wasteful number, since it uses less digits than its factorization.

21691968 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 112994 (or 112984 counting only the distinct ones).

The product of its digits is 46656, while the sum is 42.

The square root of 21691968 is about 4657.4636874591. The cubic root of 21691968 is about 278.8900274435.

The spelling of 21691968 in words is "twenty-one million, six hundred ninety-one thousand, nine hundred sixty-eight".