21738537 has 12 divisors (see below), whose sum is σ = 32563440. Its totient is φ = 14492196.

The previous prime is 21738503. The next prime is 21738539. The reversal of 21738537 is 73583712.

It is not a de Polignac number, because 21738537 - 2¹⁴ = 21722153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21738539) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 44487 + ... + 44972.

It is an arithmetic number, because the mean of its divisors is an integer number (2713620).

Almost surely, 2^21738537 is an apocalyptic number.

21738537 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21738537 is a deficient number, since it is larger than the sum of its proper divisors (10824903).

21738537 is an frugal number, since it uses more digits than its factorization.

21738537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89474 (or 89462 counting only the distinct ones).

The product of its digits is 35280, while the sum is 36.

The square root of 21738537 is about 4662.4604019766. The cubic root of 21738537 is about 279.0894614256.

The spelling of 21738537 in words is "twenty-one million, seven hundred thirty-eight thousand, five hundred thirty-seven".