21691948 has 12 divisors (see below), whose sum is σ = 38037160. Its totient is φ = 10824192.

The previous prime is 21691937. The next prime is 21691963. The reversal of 21691948 is 84919612.

It is a self number, because there is not a number n which added to its sum of digits gives 21691948.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3093 + ... + 7276.

Almost surely, 2^21691948 is an apocalyptic number.

It is an amenable number.

21691948 is a deficient number, since it is larger than the sum of its proper divisors (16345212).

21691948 is a wasteful number, since it uses less digits than its factorization.

21691948 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10896 (or 10894 counting only the distinct ones).

The product of its digits is 31104, while the sum is 40.

The square root of 21691948 is about 4657.4615403672. The cubic root of 21691948 is about 278.8899417312.

The spelling of 21691948 in words is "twenty-one million, six hundred ninety-one thousand, nine hundred forty-eight".