21263915 has 8 divisors (see below), whose sum is σ = 25541568. Its totient is φ = 16994560.

The previous prime is 21263909. The next prime is 21263927. The reversal of 21263915 is 51936212.

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

It is not a de Polignac number, because 21263915 - 2⁴ = 21263899 is a prime.

It is a super-2 number, since 2×21263915² = 904308162254450, which contains 22 as substring.

It is a Duffinian 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, 8219 + ... + 10491.

It is an arithmetic number, because the mean of its divisors is an integer number (3192696).

Almost surely, 2^21263915 is an apocalyptic number.

21263915 is a deficient number, since it is larger than the sum of its proper divisors (4277653).

21263915 is a wasteful number, since it uses less digits than its factorization.

21263915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4149.

The product of its digits is 3240, while the sum is 29.

The square root of 21263915 is about 4611.2812753073. The cubic root of 21263915 is about 277.0433579555.

The spelling of 21263915 in words is "twenty-one million, two hundred sixty-three thousand, nine hundred fifteen".