21505032440 has 32 divisors (see below), whose sum is σ = 48489976080. Its totient is φ = 8583585792.

The previous prime is 21505032431. The next prime is 21505032457. The reversal of 21505032440 is 4423050512.

It is a happy number.

It is a congruent number.

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, 556937 + ... + 594296.

Almost surely, 2^21505032440 is an apocalyptic number.

21505032440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21505032440 is an abundant number, since it is smaller than the sum of its proper divisors (26984943640).

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

21505032440 is a wasteful number, since it uses less digits than its factorization.

21505032440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1151711 (or 1151707 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 26.

Adding to 21505032440 its reverse (4423050512), we get a palindrome (25928082952).

The spelling of 21505032440 in words is "twenty-one billion, five hundred five million, thirty-two thousand, four hundred forty".