21087908 has 6 divisors (see below), whose sum is σ = 36903846. Its totient is φ = 10543952.

The previous prime is 21087889. The next prime is 21087917. The reversal of 21087908 is 80978012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21086464 + 1444 = 4592^2 + 38^2 .

It is a super-3 number, since 3×21087908³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2635985 + ... + 2635992.

It is an arithmetic number, because the mean of its divisors is an integer number (6150641).

Almost surely, 2^21087908 is an apocalyptic number.

It is an amenable number.

21087908 is a deficient number, since it is larger than the sum of its proper divisors (15815938).

21087908 is a wasteful number, since it uses less digits than its factorization.

21087908 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5271981 (or 5271979 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 21087908 is about 4592.1572272735. The cubic root of 21087908 is about 276.2768523545.

The spelling of 21087908 in words is "twenty-one million, eighty-seven thousand, nine hundred eight".