21408788 has 6 divisors (see below), whose sum is σ = 37465386. Its totient is φ = 10704392.

The previous prime is 21408787. The next prime is 21408823. The reversal of 21408788 is 88780412.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 18679684 + 2729104 = 4322^2 + 1652^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21408781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2676095 + ... + 2676102.

It is an arithmetic number, because the mean of its divisors is an integer number (6244231).

Almost surely, 2^21408788 is an apocalyptic number.

It is an amenable number.

21408788 is a deficient number, since it is larger than the sum of its proper divisors (16056598).

21408788 is a wasteful number, since it uses less digits than its factorization.

21408788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5352201 (or 5352199 counting only the distinct ones).

The product of its (nonzero) digits is 28672, while the sum is 38.

The square root of 21408788 is about 4626.9631509231. The cubic root of 21408788 is about 277.6711083883.

The spelling of 21408788 in words is "twenty-one million, four hundred eight thousand, seven hundred eighty-eight".