21372240 has 40 divisors (see below), whose sum is σ = 66254688. Its totient is φ = 5699200.

The previous prime is 21372233. The next prime is 21372269. The reversal of 21372240 is 4227312.

It is a tau number, because it is divible by the number of its divisors (40).

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, 44286 + ... + 44765.

Almost surely, 2^21372240 is an apocalyptic number.

21372240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21372240 is an abundant number, since it is smaller than the sum of its proper divisors (44882448).

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

21372240 is a wasteful number, since it uses less digits than its factorization.

21372240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89067 (or 89061 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 21372240 is about 4623.0120051758. The cubic root of 21372240 is about 277.5130096977.

Adding to 21372240 its reverse (4227312), we get a palindrome (25599552).

It can be divided in two parts, 21372 and 240, that added together give a palindrome (21612).

The spelling of 21372240 in words is "twenty-one million, three hundred seventy-two thousand, two hundred forty".