21501040 has 80 divisors (see below), whose sum is σ = 55683936. Its totient is φ = 7654400.

The previous prime is 21501031. The next prime is 21501059. The reversal of 21501040 is 4010512.

21501040 = T₂₆₃ + T₂₆₄ + ... + T₅₂₇.

It is a tau number, because it is divible by the number of its divisors (80).

It is a self number, because there is not a number n which added to its sum of digits gives 21501040.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 46410 + ... + 46870.

Almost surely, 2^21501040 is an apocalyptic number.

21501040 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 21501040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27841968).

21501040 is an abundant number, since it is smaller than the sum of its proper divisors (34182896).

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

21501040 is a wasteful number, since it uses less digits than its factorization.

21501040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 538 (or 532 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21501040 is about 4636.9213924758. The cubic root of 21501040 is about 278.0693717807.

Adding to 21501040 its reverse (4010512), we get a palindrome (25511552).

The spelling of 21501040 in words is "twenty-one million, five hundred one thousand, forty".