21771388 has 12 divisors (see below), whose sum is σ = 38724952. Its totient is φ = 10707120.

The previous prime is 21771377. The next prime is 21771389. The reversal of 21771388 is 88317712.

It is a hoax number, since the sum of its digits (37) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21771389) 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, 44370 + ... + 44857.

Almost surely, 2^21771388 is an apocalyptic number.

It is an amenable number.

21771388 is a deficient number, since it is larger than the sum of its proper divisors (16953564).

21771388 is a wasteful number, since it uses less digits than its factorization.

21771388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89292 (or 89290 counting only the distinct ones).

The product of its digits is 18816, while the sum is 37.

The square root of 21771388 is about 4665.9819973935. The cubic root of 21771388 is about 279.2299761468.

The spelling of 21771388 in words is "twenty-one million, seven hundred seventy-one thousand, three hundred eighty-eight".