21901640 has 32 divisors (see below), whose sum is σ = 49551480. Its totient is φ = 8712192.

The previous prime is 21901639. The next prime is 21901703. The reversal of 21901640 is 4610912.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 8491396 + 13410244 = 2914^2 + 3662^2 .

It is a super-3 number, since 3×21901640³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6302 + ... + 9138.

Almost surely, 2^21901640 is an apocalyptic number.

21901640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21901640 is an abundant number, since it is smaller than the sum of its proper divisors (27649840).

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

21901640 is a wasteful number, since it uses less digits than its factorization.

21901640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3041 (or 3037 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 21901640 is about 4679.9188027144. The cubic root of 21901640 is about 279.7857204108.

The spelling of 21901640 in words is "twenty-one million, nine hundred one thousand, six hundred forty".