21090008 has 8 divisors (see below), whose sum is σ = 39543780. Its totient is φ = 10545000.

The previous prime is 21090007. The next prime is 21090061. The reversal of 21090008 is 80009012.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1318118 + ... + 1318133.

Almost surely, 2^21090008 is an apocalyptic number.

It is an amenable number.

21090008 is a deficient number, since it is larger than the sum of its proper divisors (18453772).

21090008 is a wasteful number, since it uses less digits than its factorization.

21090008 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2636257 (or 2636253 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 20.

The square root of 21090008 is about 4592.3858722890. The cubic root of 21090008 is about 276.2860228885.

The spelling of 21090008 in words is "twenty-one million, ninety thousand, eight".