15681691 has 12 divisors (see below), whose sum is σ = 16611520. Its totient is φ = 14788080.

The previous prime is 15681689. The next prime is 15681703. The reversal of 15681691 is 19618651.

15681691 = 261² + 262² + ... + 401².

It is not a de Polignac number, because 15681691 - 2¹ = 15681689 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 15681691.

It is not an unprimeable number, because it can be changed into a prime (15681661) 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, 68365 + ... + 68593.

Almost surely, 2^15681691 is an apocalyptic number.

15681691 is a deficient number, since it is larger than the sum of its proper divisors (929829).

15681691 is an equidigital number, since it uses as much as digits as its factorization.

15681691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 354 (or 307 counting only the distinct ones).

The product of its digits is 12960, while the sum is 37.

The square root of 15681691 is about 3960.0114898823. The cubic root of 15681691 is about 250.3019870684.

The spelling of 15681691 in words is "fifteen million, six hundred eighty-one thousand, six hundred ninety-one".