21901537 has 4 divisors (see below), whose sum is σ = 25030336. Its totient is φ = 18772740.

The previous prime is 21901519. The next prime is 21901571. The reversal of 21901537 is 73510912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21901537 - 2¹⁹ = 21377249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21901637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1564389 + ... + 1564402.

It is an arithmetic number, because the mean of its divisors is an integer number (6257584).

Almost surely, 2^21901537 is an apocalyptic number.

It is an amenable number.

21901537 is a deficient number, since it is larger than the sum of its proper divisors (3128799).

21901537 is an equidigital number, since it uses as much as digits as its factorization.

21901537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3128798.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21901537 is about 4679.9077982371. The cubic root of 21901537 is about 279.7852818139.

The spelling of 21901537 in words is "twenty-one million, nine hundred one thousand, five hundred thirty-seven".