21906188 has 6 divisors (see below), whose sum is σ = 38335836. Its totient is φ = 10953092.

The previous prime is 21906179. The next prime is 21906233. The reversal of 21906188 is 88160912.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2738270 + ... + 2738277.

It is an arithmetic number, because the mean of its divisors is an integer number (6389306).

Almost surely, 2^21906188 is an apocalyptic number.

It is an amenable number.

21906188 is a deficient number, since it is larger than the sum of its proper divisors (16429648).

21906188 is a wasteful number, since it uses less digits than its factorization.

21906188 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5476551 (or 5476549 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 35.

The square root of 21906188 is about 4680.4046833581. The cubic root of 21906188 is about 279.8050854353.

The spelling of 21906188 in words is "twenty-one million, nine hundred six thousand, one hundred eighty-eight".