21572499 has 8 divisors (see below), whose sum is σ = 30975952. Its totient is φ = 13275360.

The previous prime is 21572479. The next prime is 21572501. The reversal of 21572499 is 99427512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21572499 - 2⁹ = 21571987 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39), and also a Moran number because the ratio is a prime number: 553141 = 21572499 / (2 + 1 + 5 + 7 + 2 + 4 + 9 + 9).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21572479) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 276532 + ... + 276609.

It is an arithmetic number, because the mean of its divisors is an integer number (3871994).

Almost surely, 2^21572499 is an apocalyptic number.

21572499 is a deficient number, since it is larger than the sum of its proper divisors (9403453).

21572499 is a wasteful number, since it uses less digits than its factorization.

21572499 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 553157.

The product of its digits is 45360, while the sum is 39.

The square root of 21572499 is about 4644.6204365911. The cubic root of 21572499 is about 278.3770869181.

It can be divided in two parts, 2157 and 2499, that added together give a triangular number (4656 = T₉₆).

The spelling of 21572499 in words is "twenty-one million, five hundred seventy-two thousand, four hundred ninety-nine".