21531501 has 12 divisors (see below), whose sum is σ = 32253312. Its totient is φ = 14354172.

The previous prime is 21531493. The next prime is 21531527. The reversal of 21531501 is 10513512.

It is not a de Polignac number, because 21531501 - 2³ = 21531493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531001) 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, 44061 + ... + 44546.

It is an arithmetic number, because the mean of its divisors is an integer number (2687776).

Almost surely, 2^21531501 is an apocalyptic number.

It is an amenable number.

21531501 is a deficient number, since it is larger than the sum of its proper divisors (10721811).

21531501 is an frugal number, since it uses more digits than its factorization.

21531501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88622 (or 88610 counting only the distinct ones).

The product of its (nonzero) digits is 150, while the sum is 18.

The square root of 21531501 is about 4640.2048446162. The cubic root of 21531501 is about 278.2006254979.

The spelling of 21531501 in words is "twenty-one million, five hundred thirty-one thousand, five hundred one".