21391700 has 36 divisors (see below), whose sum is σ = 50642592. Its totient is φ = 7778400.

The previous prime is 21391651. The next prime is 21391703. The reversal of 21391700 is 719312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8624 + ... + 10823.

Almost surely, 2^21391700 is an apocalyptic number.

21391700 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21391700 is an abundant number, since it is smaller than the sum of its proper divisors (29250892).

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

21391700 is a wasteful number, since it uses less digits than its factorization.

21391700 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19472 (or 19465 counting only the distinct ones).

The product of its (nonzero) digits is 378, while the sum is 23.

The square root of 21391700 is about 4625.1162147561. The cubic root of 21391700 is about 277.5972118360.

The spelling of 21391700 in words is "twenty-one million, three hundred ninety-one thousand, seven hundred".