21097739 has 16 divisors (see below), whose sum is σ = 24300864. Its totient is φ = 18163200.

The previous prime is 21097723. The next prime is 21097753. The reversal of 21097739 is 93779012.

It is a cyclic number.

It is not a de Polignac number, because 21097739 - 2⁴ = 21097723 is a prime.

It is a super-2 number, since 2×21097739² = 890229181824242, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21097759) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11399 + ... + 13119.

It is an arithmetic number, because the mean of its divisors is an integer number (1518804).

Almost surely, 2^21097739 is an apocalyptic number.

21097739 is a deficient number, since it is larger than the sum of its proper divisors (3203125).

21097739 is a wasteful number, since it uses less digits than its factorization.

21097739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1798.

The product of its (nonzero) digits is 23814, while the sum is 38.

The square root of 21097739 is about 4593.2275145044. The cubic root of 21097739 is about 276.3197783096.

The spelling of 21097739 in words is "twenty-one million, ninety-seven thousand, seven hundred thirty-nine".