21690000 has 150 divisors (see below), whose sum is σ = 76167806. Its totient is φ = 5760000.

The previous prime is 21689981. The next prime is 21690013. The reversal of 21690000 is 9612.

It can be written as a sum of positive squares in 5 ways, for example, as 5817744 + 15872256 = 2412^2 + 3984^2 .

It is a tau number, because it is divible by the number of its divisors (150).

It is a super-2 number, since 2×21690000² = 940912200000000, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 89880 + ... + 90120.

Almost surely, 2^21690000 is an apocalyptic number.

21690000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21690000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38083903).

21690000 is an abundant number, since it is smaller than the sum of its proper divisors (54477806).

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

21690000 is a wasteful number, since it uses less digits than its factorization.

21690000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 275 (or 251 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 21690000 is about 4657.2524088780. The cubic root of 21690000 is about 278.8815931054.

Adding to 21690000 its reverse (9612), we get a palindrome (21699612).

The spelling of 21690000 in words is "twenty-one million, six hundred ninety thousand".