21651788 has 6 divisors (see below), whose sum is σ = 37890636. Its totient is φ = 10825892.

The previous prime is 21651781. The next prime is 21651793. The reversal of 21651788 is 88715612.

It is not an unprimeable number, because it can be changed into a prime (21651781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2706470 + ... + 2706477.

It is an arithmetic number, because the mean of its divisors is an integer number (6315106).

Almost surely, 2^21651788 is an apocalyptic number.

It is an amenable number.

21651788 is a deficient number, since it is larger than the sum of its proper divisors (16238848).

21651788 is a wasteful number, since it uses less digits than its factorization.

21651788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5412951 (or 5412949 counting only the distinct ones).

The product of its digits is 26880, while the sum is 38.

The square root of 21651788 is about 4653.1481816078. The cubic root of 21651788 is about 278.7177251538.

The spelling of 21651788 in words is "twenty-one million, six hundred fifty-one thousand, seven hundred eighty-eight".