21357990 has 48 divisors (see below), whose sum is σ = 55783728. Its totient is φ = 5669568.

The previous prime is 21357983. The next prime is 21357997. The reversal of 21357990 is 9975312.

It is an interprime number because it is at equal distance from previous prime (21357983) and next prime (21357997).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21357997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27244 + ... + 28016.

It is an arithmetic number, because the mean of its divisors is an integer number (1162161).

Almost surely, 2^21357990 is an apocalyptic number.

21357990 is an abundant number, since it is smaller than the sum of its proper divisors (34425738).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21357990 is a wasteful number, since it uses less digits than its factorization.

21357990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1093 (or 1090 counting only the distinct ones).

The product of its (nonzero) digits is 17010, while the sum is 36.

The square root of 21357990 is about 4621.4705451836. The cubic root of 21357990 is about 277.4513184630.

The spelling of 21357990 in words is "twenty-one million, three hundred fifty-seven thousand, nine hundred ninety".