21531700 has 18 divisors (see below), whose sum is σ = 46724006. Its totient is φ = 8612640.

The previous prime is 21531689. The next prime is 21531709. The reversal of 21531700 is 713512.

It can be written as a sum of positive squares in 3 ways, for example, as 39204 + 21492496 = 198^2 + 4636^2 .

It is a super-2 number, since 2×21531700² = 927228209780000, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531709) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 107559 + ... + 107758.

Almost surely, 2^21531700 is an apocalyptic number.

21531700 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21531700 is an abundant number, since it is smaller than the sum of its proper divisors (25192306).

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

21531700 is a wasteful number, since it uses less digits than its factorization.

21531700 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215331 (or 215324 counting only the distinct ones).

The product of its (nonzero) digits is 210, while the sum is 19.

The square root of 21531700 is about 4640.2262875856. The cubic root of 21531700 is about 278.2014825639.

The spelling of 21531700 in words is "twenty-one million, five hundred thirty-one thousand, seven hundred".