21601540 has 12 divisors (see below), whose sum is σ = 45363276. Its totient is φ = 8640608.

The previous prime is 21601519. The next prime is 21601561. The reversal of 21601540 is 4510612.

It is an interprime number because it is at equal distance from previous prime (21601519) and next prime (21601561).

It can be written as a sum of positive squares in 2 ways, for example, as 13660416 + 7941124 = 3696^2 + 2818^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 540019 + ... + 540058.

It is an arithmetic number, because the mean of its divisors is an integer number (3780273).

Almost surely, 2^21601540 is an apocalyptic number.

21601540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21601540 is an abundant number, since it is smaller than the sum of its proper divisors (23761736).

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

21601540 is a wasteful number, since it uses less digits than its factorization.

21601540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1080086 (or 1080084 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 21601540 is about 4647.7456901169. The cubic root of 21601540 is about 278.5019484213.

The spelling of 21601540 in words is "twenty-one million, six hundred one thousand, five hundred forty".